Nice work on getting everything done for a game jam.
At first I kept worrying I would run out of "shots" or the sharks would return, but when I realized I had as many shots as I wanted and the sharks never came back it felt a little too easy. Maybe limiting ammo or having sharks randomly show up would add some suspense.
Otherwise, solid mechanics. Cute idea. I liked that I was protecting a little minnow.
Good luck in the jam!
D