The perfect kind of game for a game jam, simple to understand, not time-consuming, charming, and most importantly creative and fun!
Kinda makes me feel bad that my random attempts were better than my thought-out attempts, overall I got 52% after 7 tries.
I feel like having 1 or 2 fewer sponges would allow you to reach some higher scores but the added difficulty that comes from having to place more sponges is not something I'd be afraid of.
Thankfully my team and I didn't go for a packing problem game like I initially suggested. It would have been hard to compete with your game.