Underwater self propelled scooter devices

[Elgin Clock]

I bought one of these off woot.com the other day (Yes, I'm still asking myself why I bought it. Idk. It looked like it would be fun. - Blame it on an impulse buy & I love having cool toys.)

http://www.geeks.com/details.asp?invtid=DWS1502&cat=CON

Just wondering if anyone has had any experience with these things?
Suggestions, tips, tricks, comments?
If I let go of it underwater, would it float, or sink? lol

Apparently from what my Scuba Diving friends tell me (besides the fact that they want to steal it from me to try out) the 98' depth limit and 3mph speed on the thing is pretty good, and it seems like a great buy for the price. (Less than shown on that page in the link above by a considerable amount).

[Taylor]

It would be a very fun toy to have - rarely do recreational divers go below 80 feet. Does it have variable speed, or is it a choice between 3mph and 0mph? I would imagine it could extend dive times by as much as 1/3. Unfortunately, I could see recreational divers/snorkelers causing serious physical damage to themselves or to the habitat if they do not know the limitations of the machine or of themselves. Take only memories, leave only bubbles!

[Elgin Clock]

Originally Posted by boiler

Does it have variable speed, or is it a choice between 3mph and 0mph?

Originally Posted by Website

Other features include dual speed, auto shut-off, positive buoyancy, protective safety grill and up to 1-1/2 hours of run time on a single charge.

I haven't gotten the item yet, but as soon as I do, I'm going to let my Scuba Diving friends take a look at it first and analyze it for me to see what this bad boy can do.
I'll be sure to post some results of testing/playing and some pics as well I'm sure.