Help with Pygame sprite collision

[Dan_1]

Hello everyone, I'm hoping somebody here can help me out. I'm fairly new to Pygame, and to programming in general. I'm planning on trying to make a Frogger style game, and I'm not really sure hoe to do the water part of the game. For anyone who doesn't know what I mean, there is a part of the game where you have to jump across logs that are floating across water, and if you hit the water you die (doesn't really make sense, frogs can swim!). Anyway, my question is this-if I was to just draw the water as one big blue retangle and make it a sprite, it will still sense a collision between the frog and the water even if the frog is on top of the log which is drawn on top of the water (thats a mouthful!). So how can I get around this? I was planning on making the log a sprite as well so that the frog can move at the same speed as log when he's on top of it, but won't the program still sense a collision between the frog and the water? I'm not sure how to do this, any advice would be very much apppreciated.
Thanks!
Dan