Fun concept!
You don't see spatial awareness puzzles often and watching the sponges grow is very satisfying. I think its a good fit for the theme of the jam.
Feedback: It is pretty hard to tell where you placed sponges on the previous run and I think the game would be greatly improved with the ability to see where you had placed the last batch. Additionally, I also think a reset button would not be a bad idea in case the player miss clicks.
Visually, I think the game is very readable and its easy enough to understand what is working or not working with growing the sponges but not so easy that the solution is immediately apparent at a glance. The sponge growth felt fair and behaved as expected. I was never left thinking a sponge should have grown more than it did. As a side note, the benefit of the sponges and the water as a motif is it makes it really clear exactly how well you did visually and I think that was a really good call.
Overall, good work!