The Fantasea NanoFlash is a very small "flash in a box" strobe. Although small, I've seen some nice shots taken with it; mostly close in and macro, but for what it is and what it costs it can work surprisingly well; especially in clear water with small P&S cameras. Not very adjustable, it has 3 steps of power and some diffusers. Uses 2x AAA batteries.
BUT, it's not suitable for the G10/11 as it doesn't have anywhere near enough power or coverage.
Their Remora strobe is a big step up in power and adjustability; but a 60 deg. beam angle - even with a pretty nice lens and diffuser, leaves it short. I also noticed that there is quite a bit of vertical fall off with it on wider angles. But if you're more interested in macro and on a budget - it's not at all bad.
With strobes you pretty much get what you pay for and uw - it's all about light.
Again, I like the Sea & Sea YS-27DX or YS-110a strobes. Wide beam angle, adjustable, awesome build quality, powerful.
Jack