Two thoughts in response:
First, my girlfriend has used those. Yes, the camera works. However, for the pix to be "good" they have to be taken in really shallow water -- less than 15 feet -- near mid-day on a sunny day, and you have to be close -- no more than two arms lengths -- to your subject (a good rule of thumb for most U/W photos).
Second, as regards disposable cameras for U/W photos, one that I have a love/hate relationship with.... Ikelite used to make a housing called the Aquashot housing that accepted 27 shot cardboard disposable cameras. The Aquashot kit included an external slave strobe on a plastic arm, a flash deflector to block the disposable camera's flash (and thus reduce backscatter), a flash diffuser and macro lens attachment. My Nikonos-toting friends pooh-poohed the Aquashot set-up for a lot of reasons (e.g., the plastic lenses), but honestly, I got some excellent U/W shots with it. You could use it in drive-by P&S mode, or take your time, compose the shot, get close, etc., and get good color print photos. And, by varying the plastic shims in the case, you could get it to accept a variety of cardboard cameras.
The Aquashot has some downsides:
- stuffing it with disposable cardboard cameras costs more than dropping in a 36 shot roll of color print film, and way more than dropping bytes onto an SD card.
- everything is pre-set, so you have no control of aperature, shutter speed, flash, etc.
- the external flash is fixed in position. If you want it anywhere other than above and to the left, you have to unhook it and manually hold it at the right angle for the subject, tough to do while hovering close to your subject and manipulating the camera at the same time.
- AND -- this was the one that drove me batty -- if the cardboard camera wasn't positioned juuuust riiiight in the housing, the controls didn't work. You couldn't advance the film, or the shutter release wouldn't work, or you couldn't turn on the camera's built-in flash, etc. This didn't happen all the time, just often enough to make me crazy. You could guarantee that the dive when the Aquashot wasn't working was the dive where the manta would swim past, or a school of squid would surround you, or you'd find 4 scorpion fish, etc.
- finally, I think Ikelite discontinued the Aquashot. You can probably find them on eBay, though. I've still got a couple -- bought three of 'em last year when a dealer closed them out, cannibalized them to make two good systems, and have a spare housing and strobe.
BTW, even if you don't use the Aquashot housing for anything, the strobes make reasonable slave fill-flashes for lots of shots.
Still, before I bought my first "real" U/W camera system, I used the Aquashot on maybe 10 dive trips, and got good results most of the time.
Bottom line on disposable U/W cameras IMHO: just like topside, the most important ingredient is the eye behind the camera. Once you develop that, you can take decent to good shots with any camera system you know how to operate.