I would recommend the
Olympus TG-2iHS, following OP and their main use for snorkel and requirement for no case. It's rated at 15m (50') without the need of external case and has various underwater settings one of which is for shallow water. A friend has it and has taken GREAT pics while snorkeling. Shutter speed is really fast and has variable focal length at a touch of a button.
The price has dropped since it's release, initial MSRP was $399 and is now down to $350... it's upgradeable with 2 waterproof lenses, a telephoto lens that expands the zoom range by 1.5x and a fisheye lens for wide angle shots. Also features GPS and Compass funtionality.
GoPro wouldn't be a good choice since it has to be used with housing and pictures are hit/miss. I own it and have to use burst 5/1sec and pick the best out of 5, very time consuming and tedious. It's shutter speed is really slow, kinda of a surprise for an action cam... It's more for taking video and taking advantage of it's high resolution capabilities.
Other option would the
FujiFilm FinePix XP200, also rated to 50' waterproof. It's cheaper since it lacks many of the "cool" features that the Olympus has. CNET did a stress test with both TG2 and XP200 and the XP200 won by being able to go way beyond it depth rating.
You can check out different rugged point and shoots in the DPreview 2013 RoundUp that has comparison table and in depth review of their top picks for rugged and all around cameras.
The
Nikon AW-1 previously mentions looks awesome but it's introductory price is really high, MSRP $996 with both lenses. It was just released into the market and there isn't that many reviews regarding quality build, it would suck if such an expensive camera had flaws but then again its Nikon and they're not that known for faulty devices.
In my case, I'm going for either the TG2, since it has UW options and underwater case to expand its depth, or the E-PM1 that has exchangeable lenses. Was initially going for the Nikon AW-1 but it's way out of my budget and it's under water case is almost the same price as the camera..