A man floating on a tube on a lake.
A person is at the lake.
Being on a lake is same as being at the lake
exists e1 x1 x2 x3 x4.(a_topic(x1) & on(e1,x4) & n_lake(x4) & on(e1,x3) & n_tube(x3) & Actor(e1,x2) & v_float(e1) & (x1 = x2) & n_man(x1))
exists p1 x1 x2.(n_lake(x2) & at(x1,x2) & n_person(x1))