What I should look for is not underwater cameras but snorkeling cameras! 

2014 buying guide to the best snorkeling cameras

http://www.tropicalsnorkeling.com/waterproof-digital-snorkel-cameras.html  

Panasonic TS25 is good enough!  Olympus Tough TG-3 is overkill.

Best Underwater Compact Cameras for 2015:  <1>   <2>


Update (12/2015): Panasonic DMC-TS30 - Bought for $99

Pictures taken by TS30: <1>   <2>   more

Spec: 1/2.33-inch CCD Sensor.  (cf.  Canon Elph 100 HS : 1/2.3 inch - 28.0735mm2 (6.17mm x 4.55mm) so about the same)

Battery: DMW-BCK7

Beautiful Underwater Shots 
The red color reproduction of Advanced Underwater Mode easily compensates for the red tones which are easily lost in underwater shooting to create more natural underwater images.  Additional action modes include Sports, Snow and "Beach and Surf.

Creative Panorama 
With the Creative Panorama function, you can shoot and overlay consecutive horizontal/vertical images, then add filter effects with Creative Controls. 

Time Lapse Shooting 
Position the camera to record stationary observation for flowers coming into bloom, scudding clouds and other subjects. A series of successive images can be combined in-camera to produce time- lapse video. 

Torch Light 
Torch light helps record beautiful videos even in dusky underwater environments or in camp at night. And even when camera functions are inactive, you can turn the light on to illuminate subjects.  src


So what are the drawbacks of buying one of these waterproof digital snorkel cameras?

First, these cameras all have little compartment doors (for access to batteries and memory cards), often more than one. And the waterproof seals on these tiny doors are very small and delicate (compared to a regular underwater housing). If one fails, your camera is ruined. Based on the reviews I have seen of almost all of these cameras, you run a good risk of a failure if you snorkel a lot. They just are not as robust, and they need to be. We really bang our cameras around at times.

If you are very careful with the seals, keep them clean, and don't hit the doors underwater, they may work well for years.

The second important thing to note about most of these waterproof digital snorkel cameras is how small their lenses are compared to most compact cameras. A small lens means a small sensor. And the combination means lower image quality. Even an inexpensive compact camera with a separate underwater housing will likely give better image quality because of the lens/sensor size. There are a few exceptions though.

So if you plan on using it often I would steer you towards the next step up in a snorkeling camera.

- See more at: http://www.tropicalsnorkeling.com/waterproof-digital-snorkel-cameras.html#sthash.wbHjtbfO.dpuf

In fact, according to the above link, it argues that "an inexpensive compact camera with a separate underwater housing will likely give better image quality".  So, in the next step up in a snorkeling camera, it recommend Canon Elph 100 HS!

Or Canon PowerShot ELPH 320.   According to here, there is no waterproof housing for 320 and 330.

http://www.usa.canon.com/cusa/consumer/standard_display/underwater_photo :  No housing for ELPH 320?  Only has WP-DC320L for ELPH 300.

Decision on 1/3/2015:  Canon Elph 100 HS & WP-DC310L Underwater Case.  Also buy float strap & extra heavy-duty battery.

Get A Float Strap

Note that most of the cameras above are waterproof, but they don't float. Lots of folks have watched them sink to the depths.

So one of the most popular accessories to buy with one of these is a float strap like the one at right.

- See more at: http://www.tropicalsnorkeling.com/waterproof-digital-snorkel-cameras.html#sthash.wbHjtbfO.dpuf

2013 Waterproof Camera Roundup Digital Photography Review

Panasonic Lumix 16.1 MP Rugged Waterproof Digital Camera (DMC-TS25)

  - Waterproof to 7 m

  - Video made with the Panasonic LUMIX TS25 camera and an ALZO Snorkel-Pod monopod. The location is Honeymoon Beach on St John USVI.

  - Groupon $120   spec 

  - Amazon white color $120    2/27/2014

Olympus Tough TG-2

  - best 2013 snorkeling P&S.  With a fast f2.0 lens, and an impressive depth rating of 50 feet.  Video Test.

  - Another unique feature of the TG-2 is the ability to add conversion lenses. The camera supports both telephoto and fish-eye lenses. As you'd expect, both of these lenses are waterproof. The conversion lens adapter that comes with these lenses (and can be purchased separately) also allows the use of 40.5mm filters.    dpreview

My impression:  Panasonic TS25 video look vey nice so good enough.  For all-around and better performance, spend $200 more on TG-2.

Note: The WP-DC310L Underwater Case ($70) (Amazon; B&H) has been specifically designed for the Canon PowerShot ELPH 100 HS Digital Camera and is waterproof down to the depth of 10 ft.

Weakness of WP-DC310L:
(1) "I noticed that the zoom [tsiu: really?], auto/manual setting [tsiu: don't need; always set to underwater setting], play photos, and even the near/far buttons do not work with this case. src
(2) "because the housing is so air tight, my battery overheated a lot"  src

Review:

(1) This case was great for our trip to Mexico since we did a lot of water activities. Very easy to use and fits the camera like a glove. I love that I could still zoom and edit and use all of the camera's features while the waterproof case was on. Photos were clear... Just be sure to shake or wipe off the outside before shooting because water droplets may cover areas in the pics. 
Pros:
Easy to use
Convenient
Fits camera perfectly
You can still use all of the features( zoom, etc)
Took great, clear underwater shots.
Cons:
A little bulky ( but that is necessary to use the zoom)
You have to remove the camera's wrist strap before putting in the case, so when you use the camera without the waterproof case you will have to put the wrist strap back on every time.
Overall, so happy that I purchased this case!! :-)

Pictures and video on Web from Canon ELPH 100:  <1> (e.g., this beautiful Trumpetfish: <1.1>)


<1> Best Underwater Compact Cameras for 2013

Best Entry Level Camera
The GoPro Hero 3 with the Backscatter Flip3 Color Correction Filter
Camera & Housing starting at $199

GoPro Hero 3 White Edition $200
GoPro Hero 3 Silver Edition $300
GoPro Hero 3 Black Edition $400
Backscatter Flip3 Filter for the Hero 3 $69
Backscatter GoPro Hero 3 Starter System with Sola 500 $862
Dive Housing for GoPro Hero 2 $39
Backscatter Flip2 for GoPro Dive Housing $49


Best Entry Level Mirrorless Camera
The Olympus PEN Series
Camera & Housing starting at $1447

Olympus changed the underwater compact camera landscape forever with their launch of the PEN series of cameras with underwater housings which we first reviewed in 2010. Now in its fourth generation, the PEN is better than ever with a more advanced E-PL5. This camera offers a step up in terms of flexibility, image quality, and growth potential, all at a point and shoot price point. After shooting the E-PL5 early in 2013, we think it's the best value in underwater photography today.
Olympus E-PL5 PEN Camera with 14-42 Lens $700
Olympus PT-EP10 Housing for the E-PL5 $747
Backscatter PEN and Sea & Sea Strobe Package $2118

<2> Olympus PT-EP01 Underwater Case for PEN E-PL1 Digital Camera (Rated for a Depth of 40m) 

Amazon.com  $400 (3/2013)   $250 (2/2014)

The PT-EP01 underwater case has been especially customized for one camera of the PEN family, the E-PL1. It is the world's first waterproof housing for a Micro Four Thirds camera. The extreme light weight PT-EP01 (only approximately 1100g, just half as much as the PT-E06) is waterproof up to a water pressure equivalent to a depth of 40 meters. As a genuine advantage to the underwater photographer, you can make use of the Live View function on the one hand, but it is also possible to attach the electronic Viewfinder to the E-PL1 and use it underwater. Additionally the PT-EP01 has a small, but very important feature at the backside cover. The back is semitransparent and has a further monitoring window just below the LCD window, which allows you to detect any water leakage before having serious material damage. The PT-EP01 has a fix lens port and supports the use of the M.Zuiko Digital ED 14-42mm 1:3.5-5.6 (How about my Panasonic 14-42mm lens?  Autofocus still work?) and the M.Zuiko Digital ED 9-18mm 1:4.0-5.6 (very expensive!). Besides the possible flash connection the PT-EP01 offers the use of a macro lens adapter (PMLA-EP01) to attach the macro lens (PTMC-01) for special macro photography. The high quality underwater photography is additionally strengthened through the underwater macro and underwater wide shooting modes of the E-PL1.
Product Description:
Waterproof up to 40m
Front cover and back cover, locked by a rotary buckle
Two optical fiber connectors
Monitoring window to detect water penetration
Large buttons for easy operation
Multi coating glass to reduce inner reflections

Review 1: 
... a package that was light, yet with possibilities of having near professional level options.

Both the E-PL1 camera and the PT-EP01 fit the bill perfectly. Shooting in RAW with no extra light made it possible to correct for the lack of color on 20m, although a flash is recommended.

Review 2
As a staring point I used the following basic settings on the E-PL1 for my tests, ISO-200, auto white balance, adobe raw files, Image Stabilization-1, ESP metering, single frame advance, single and continuous AF, RC mode off (this would be turned on when using the Olympus UFL- strobes), images were exposed shooting in both TTL and manual. I have found the optional VF-2 electronic viewfinder to be an outstanding option above water but it is of little use in the PT-EP01 housing because your eye is just to far back from the viewfinder while wearing a mask. The VF-2 would work very well if an accessory like the Inon 45 degree accessory viewfinder could be added to the PT-EP01 housing.
The PT-EP01 is a clam-shell style housing (e.g. front section and door held together by a hinge) made from high-grade polycarbonate. It is smaller in design but very similar to the well-regarded Olympus PT-E05 and PT-E06 housings for the E-510/520 and E-620 DSLRs. The housing has a large hinge on the left side when viewed from the rear and a rotary buckle locking device on the right which locks the housing with a firm counter-clockwise turn. The rotary buckle can be released by depressing a red locking button and turning it clockwise. This rotary style locking system has been used on many Olympus housings with great success and is very easy to use and maintain. The rear door has a single O-ring which seals the housing and prevents leaks. As always this o-ring should be removed, cleaned, re-greased and re-installed after each diving day. Like all the current Olympus housings the PT-EP01 is rated to a depth of 130 feet (40 meters), the maximum recommended depth for recreational sport divers. I have pushed that limit to 150 feet (46 meters) without issues to structural integrity or loss of push controls. The housings rear door has twelve well labeled push buttons for all twelve push button controls on the rear of the E-PL1 camera, a push button to activate the optional VF-2 electronic viewfinder and a rotating dial to control the mode wheel on the top of the camera. The top of the housing has the on/off push bottom and the shutter release lever which is presses down from the top rather than being pulled like a trigger. I found this a little awkward at first when using a try with grips. Once you hold the right side of the housing with your right hand and use the grip as a wrist support tripping the shutter becomes much more comfortable. On the left front of the housing viewed from the rear is the focus/zoom dial which is 30 mm in diameter. This dial is used to zoom lenses and could be used as a focus dial as well for fixed focal length lenses like macros. Using a tray with a grip on the left side my index finger is in perfect alignment with the zoom dial and rotating it with light weight dive gloves is a breeze. With my dry suit gloves the zoom control will be more awkward to turn. Next to the zoom dial are two optical ports for use with fiber optic strobe cords.

When the PT-EP01 housing was introduced by Olympus it was advertised as a “fixed” port housing a non-removable flat port for use with the Olympus M. 14-42 mm and M. 9-18 mm zoom lenses. While these two lenses cover a wide range of possibilities and would appeal to any new comers to underwater photography, the Olympus flat port will limit the wide end of the M. 9-18 mm zoom and give less than stellar results. This is an excellent entry-level system at a very appealing cost. 

This article mainly focus on still photography but I did do some video clips with the M.14-42, M. 9-18 and Pany 7-14 zooms. With the kit lens you can hear a little noise in the sound track when the lens re-focuses on a moving subject with the more expensive zooms no focus noise was detected. I shot A/V light in 8 to 12 feet (2.5 to 3.5 meters) of salt water. I am not a capable videographer so I will leave further comments on the E-PL1s video prowess to other more knowledgeable journalists.

With the Olympus port and kit lens the housing is buoyant by a few ounces in salt water. This is not a bad thing at all, I found that by the time I added a tray/ grips and some lighting it was one of the most well-balanced systems I had ever used. With its light weight and small size I was able to use the system for hours underwater, mostly holding it with one hand and not end up with a sore wrist at the end of a days diving.  

Review 3

The housing allows space for the optional electronic viewfinder, but due to the high resolution LCD screen on the back of the camera, we found the electronic viewfinder unnecessary. Unfortunately this additional viewfinder space makes the housing taller than it needs to be, but the extra air space gives buoyancy to the system and makes it near neutrally buoyant in water and easy to swim and shoot with one hand.

One nice touch that was not present on previous PEN bodies is a dedicated movie button, allowing the user to start recording at any time. The shutter release also has a great feel, allowing the user to feel half press even with dive gloves. 

Camera installation and removal is a breeze. There's no camera tray like SLR housings and the camera just easily drops into place on rubber guides. The latch system has a lock to prevent accidental opening. Many new shooters have commented that they like the clear back door as it allows them to see the o-ring and verify any leaks at the beginning of the dive.

Our critiques on the PT-EP01 underwater housing

It’s important to remember to pop up the cameras flash prior to putting the camera in the housing. There is no way to pop the flash up underwater. Since the pop-up flash is required to trigger your underwater strobes, forgetting this step can be a deal killer on an important dive.

The zoom gears are of a flexible but firm material that is easy to install on the lens. However, the zoom knob on the housing is just stiff enough and positioned is such a way that one finger operation isn't possible. While we didn't find this problem a huge issue in our tests, cold water divers and frequent zoomers should take note.

Review 4: 

 Just remember that the flash cannot go off underwater (? even after popping up?) on the PEN EPL1 so you'd have to get an external flash as well. 

<3> Panasonic/Leica 45mm Macro in the Olympus PT-EP01/03 Housing for Oly E-PL1/2

<4> 10bar    manual   mirror   very expensive!  

10Bar HS-DC-Op-EPL1 

Underwater Housing for E-PL1 


Olympus PT-EP01 Underwater Case for PEN E-PL1 Digital Camera (Rated for a Depth 
of 40m) 
 
- The PT-EP01 has a fix lens port and supports the use of the M.Zuiko Digital ED 
14-42mm 1:3.5-5.6 (How about my Panasonic 14-42mm lens?  Autofocus still work?) 
  So may need to buy the M.Zuiko 14-42mm. 
  Note:  And this build-in port does not work well with M.Zuiko 9-18mm.  Wide 
angle lenses like this the behind the flat port exhibit refractive 
magnification, radial distortion, and chromatic aberration. 
(http://zenunderwater.com/products.php?prodID=5) 
 
-  Unlike many housings that come without a dome port (different lenses may 
require different domes), the EP01 comes with a port. Many early reviews and 
descriptions on the web said that the EP01 port was not removable and even the 
Olympus store says the housing has a fixed lens port, but it is, in fact, 
removable. That's not immediately obvious as it requires removal of a screw and 
retainer clip, but then the dome rotates off. The folks at Zen Underwater offer 
the WA-100-EP third party port (http://zenunderwater.com/products.php?prodID=5) 
that replaces the Olympus flat port with an optically coated glass dome port 
that guards against distortion and aberrations, and offers a wider field of 
view. Other third party domes will undoubtedly follow. 
 
 
- cleaning equipment? 
    "As always this o-ring should be removed, cleaned, re-greased and 
re-installed after each diving day." 
 
- no need external flash for shooting picture: 
    Shooting in RAW with no extra light made it possible to correct for the lack 
of color on 20m 
  How about movie? 
 
- Need a Underwater Zoom Ring for zoom lens 
    Olympus PPZR-EP01 Underwater Zoom Ring - for M.Zuiko 14-42mm (I, not II) 
    Olympus PPZR-EP02 Underwater Zoom Ring - for M.Zuiko 14-42mm II / II R  and 
M.Zuiko 9-18mm 
    Visit "Geoff Brownell at Mullen" 
 
http://scubadiverinfo.com/3_cameras_olympus_pl1.html 
 
 
Conclusion: 
Need to buy minimum: 
- Olympus PT-EP01 Underwater Case          $250 
- M.Zuiko 14-42mm (I, not II)              $95  (Used)  - http://www.amazon.com/gp/offer-listing/B002CGSYLW/ref=dp_olp_used?ie=UTF8&condition=used 
- cleaning equipment 
- Olympus PPZR-EP01 Underwater Zoom Ring   $45 

More:

Zen Underwater FP-100-EP Port for Panasonic 45mm in Olympus PT-EPxx Housings - $439.00

http://www.backscatter.com/learn/article/article.php?ID=100 

http://thewirecutter.com/reviews/beginners-guide-to-underwater-photography/#best 

6/2015:

Xiaomi Yi Xiaoyi Action Camera WiFi 16MP 1080P 60FPS Ambarella A7LS 155 Degree Wide Lens Bluetooth 40M Diving 

US$ 72.99

Highlights

Cnet:

The Yi is unabashedly a GoPro knockoff, albeit one with a Sony image sensor and an Amabarella chipset like the one that powers the GoPro Hero3+ Silver.

It can capture 1080p video at up to 60 frames per second and single-shot or burst-mode 16-megapixel images. It features a microSDXC slot for storage and Micro-USB and Micro-HDMI ports. And it has Wi-Fi, which lets you link to the camera via an Android or iOS device to modify settings, live-stream video and so on.


Mangrove Electrical Heater Neoprene Vest DEH V

The Mangrove DEH-V is a state of the art power heated undersuit, that allows to turn any standard wet and drysuit in to a much more comfortable heated suit. 

Worn underneath a wetsuit, it creates a thermal layer between the body and your wetsuit for a much more pleasurable and warmer diving experience. 

The system warms to 42º C using any of the available battery packs and keeps the core body temperature warm. Its unique rubber heating element technology guarantees that it is completely safe totally immersed in water. 

One size for men and another for women fit all. The DEH-V can be used with drysuits by means of the drysuit bulkhead connector CEH-DS.

 

Mangrove Re Usable Chemical Heater DCH V

 

Re-usable chemical heater integrated in a neoprene vest compatible with wet and dry suits. The heat pack contains a liquid solution of sodium acetate in a sealed bag 

Flexing the stainless steel “trigger” within the sealed container causes a single molecule of liquid to crystallize which starts a chain reaction causing the entire solution to change from liquid to a solid. 

This phase change causes the pack to heat to 54ºC (130ºF), and the generated heat will last up to 30-40 minutes. By placing the pack in boiling water, the crystals are returned to a liquid state, this process can be repeated hundreds of times.