This movie is the second version of fish school asset using thinking particles.Shark movement is still wired :-)
In this time, sharks movement is controlled by "Shark target" particle. Sharks start to attack fishes at certain timing. This timing is decided by random number to "Shark target" from 0 to 100 using random helper (frame/iteration) then if the number exceed certain threshold(for example number is between 98 and 100), "Shark target" changes to "Shark target active" then go to fish leader's direction. Once "Shark target active" is close enough to "Leader", "Shark target active" will get back to "Shark target". "Shark target" itself is controlled by turbulence wind and vortex.