They are supposed to be top notch (as long as you buy from a reputable company with a good track record) Only problem is they require batteries, which require electricity to recharge. Yes I know you can us non rechargeable batteries, but that might get real expensive.

On the other hand I have seen some that has a handle you crank to supply the power for the bulb to do it's thing. Then again, for that to work, you need real clear water to start with.