I have a 12 volt Power Snorkel that floats behind you when you are diving. It allows you to dive around an away from the boat. We have just been on a trip to the Great Barrier Reef in Australia and used it extensively and found it easy to use and have had no problems.
Battery life is a bit over an hour on a charge. We have a spare battery and can charge the batteries in a socket in the boat, though battery charging is slow.
The quoted 6m with two diver and 12m depth with one diver is conservative. We can dive to about 8-9 m with two divers though the air gets thinner.
We purchased it in Australia and they can be seen on the following web site
(owner Hanse 540 "Moksha" Sydney Australia)