Simple mechanics but still challenging and entertaining. I think my favorite part was watching the mountainous dam keep growing and growing to crazy proportions and then just cartoonishly falling over on top of the river.
I think a little more depth added to the gameplay loop could've been a welcome addition, but for game jams I understand and respect staying close to a small scope for your game.
Overall, the game looks and sounds great, and traversing the river offers a good amount of challenging without being too punishing. Nice work on this one!