Thanks! Yes some levels can get a bit intense and some waves could use a bit of fine-tuning. Maybe at some point I can also add a difficulty option.
About the fish power, the currently selected one gets highlighted (it flashes and has a little animation) but the effect is not always very visibile so I should probably improve that and indeed you're right that it would be good to be able to swap power, I'll keep this in mind for future updates!