Here are four fish I made for four prospective upcoming levels. Art isn't my specialty, but at least I feel like I got the expressions right. The black shadow part is the kaiju form that scales up. If you stop each fish from mutating into a kaiju for long enough, it swims away, saved, and the next one will come. The seahorse is probably going to be the most challening, due to its size and the waypoints I'll give it.
There will also be a limited use "de-mutate" power for the robot fish that you'll be able to acquire in a simple store interface.