Combat is good enough and your timing twist is fine, it was perfect for the jam.
If you expand on it I'd say that in this kind of real time games what can be fun about it too is fighting enemies under doors, make them fall into a pit by stepping on a plate at the right moment, in your case you can have harpoon traps underwater that the player has to avoid but can then be used to their advantage to damage enemies, maybe something triggering mines is possible too although I can't think of a good way to do it right now.
I forgot to mention the enemies' name in my previous comment, giving cute names to things you're going to smash is rude and hilarious, I love it.