A group of people mill around while a man in a fish costume descends a staircase.
no one is in a costume
Dressing up like a fish is a costume.
exists e1 p1 s1 x1 x2.(exists e2 x3 x4 x5 x6.(Theme(e2,x6) & Actor(e2,x3) & v_descend(e2) & n_staircase(x6) & in(x3,x4) & n_costume(x4) & of(x4,x5) & n_fish(x5) & n_man(x3)) & while(e1,p1) & a_around(s1) & Manner(e1,s1) & Actor(e1,x1) & v_mill(e1) & of(x1,x2) & n_people(x2) & n_group(x1))
-exists p1 x1.(exists x2.(in(x1,x2) & n_costume(x2)) & n_one(x1))