slr is the "pro" type camera, with the interchangable lenses.
slr is single lens reflex. theres one fixed lens (removable), passes through to the mirror inside (dont touch that...).
provides better quality images due to a better (most of the time) image sensor.



the other is a point and shoot/compact/fixed lens camera. still great, but lacks depth.


finding a waterproof slr isnt going to be.

other key things to consider:


FPS:
if you plan on getting creative with speed, maybe something over 3.5 fps (frames per second). stores more images in the buffer, meaning faster saves to memory card.


Higher ISO:
all SLR's are going to have incredible manual controls where you can set shutter speeds and ISO.
something with a high ISO is great. 3200 ISO would be ideal, but remember, the higher the ISO setting you use, the more noise (grainyness) you'll get when you zoom on the photo. ideally, use less iso and leave your shutter open longer.


hmmm...what else am i missing...