Add the FishManagerBP to your scene, open fish manager and in the default settings, at the top, you can select multiple classes of those fish, and how many of them. You have to use FishManagerBp to do , as the fish wont do anything, or will crash the editor (Another user and I both experience crashes)
As for the boats, I know for a fact the Man-O-War is drivable, and the cannons work. You could easily copy the blueprint nodes from that and put them into the smaller boat.
(Open the project setttings and check the inputs, or open the Man-O-War BP and check them there. I believe they are defined separately in each bp
Also to play with the physics rope, just grab with your left mouse button and “swing” and release. Have fun watching two boats ping pong like crazy
Also, the breakable rope, same thing, but if you “swing” hard enough, the boat will break free… but when you swing it that hard, it flys into space…