Last time I went to the seaside, it was at the end of october, I did not have a swimsuit, but I ended up in the sea anyway. Yeah, I love to get in the water!
Now imagine how much I would like to take photos in (and under) the water, just like Sarah Lee. I would love that!
Going underwater opens to a whole new (blue) world. To access it, you need new equipment. Expensive equipment.
If you want to use your dSLR, the housing to go underwater will cost you at least $670, that's the cheapest I found and it goes way above. It costs as much as the camera itself...
So, you'll probably be willing to look for a cheapest way, unless you are really serious about this. It turns out the cheapest housings start at $100, for the Nikon Coolpix L10 & L11. These may not be the best compact cameras but you can find used ones from $35! That means for less than $150 you can start exploring the land of Poseidon. Of course, once you get better and go further, you can spend more money and buy yourself top-notch equipment.
Places where you can buy underwater equipment: