I have been using the MASH flight node settings to create schooling effects for the fish in certain scenes, but after having some trouble with it because of the different amount of fish I have it didn't work out how I wanted it to look (see below). Due to early tests being really static and motionless despite the motion path, I added 18 separate rigs into the fish and skinned them so that the tail could wiggle, then keyframes them to loop continuously. The test above included 4 motion path curves and two sets of fish at different heights and sizes to replicate the schooling effect of MASH, but I like this effect more as I have more control of it and can change things easily.
(Schooling test gone wrong)
I have also been refining the timing of my scenes and changed them so that each scene where we visit the jellyfish and crab will be 25-30 seconds. The intro will possibly be shorter and the last scene the longest.