Don't bother. The quality of the images is dreadful and the integrity of the "bag" systems is worse. You are taking a major risk by placing over $1000USD in a plastic bag.
If you are interested in underwater photography, you are going to have to lay out some money. The entire underwater kit I have costs way more than the camera/lens I am using (30D with various lenses). But I am 100% confident in the integrity of the housing. If there is a failure, it will be because I failed to seal the housing correctly, not because the housing failed.
If you only want a basic set up, buy most any of the small Canon point and shoot cameras for which Canon makes an underwater housing. The G-series cameras make pretty nice underwater systems in a Canon housing. I have both a G-7 and G-9 in Canon housings. They aren't up to the caliber of an SLR in a housing, but especially for snorkeling, they are great. Any of the other small Canon's would probably work well, too.
The Canon housings sell for about $150USD here in the US. Add the price of the camera and it will probably set you back $400-500USD or around 350 euro.
Best advice? Don't use one of the bags. Get a camera with a proper underwater housing.
EDIT: Was just looking at the Canon D10 and the Olympus Tough series. Found several good reviews of the Canon and people seem to like the Oly cameras as well. If you are going this route, get a camera rated to at least 10 meters. You can surface dive to greater than 3 meters easily, and those devices only rated to that depth will surely give up and leak. I still think a point and shoot with a proper housing is a better choice, but the D10 looks pretty good.