% Set up initial data for fish1
     disp('Initialize data for simulating fish under external current')
     nfish = input('Input number of fish (10 is reasonable): ');
     zoom = 20;
     fishp = (2*(1:nfish)/nfish)-1;
     fishv = sqrt(-1)*fishp;
     fishm = 1+((1:nfish)/nfish);
     tfinal = 10.;