A man is riding a board and jumping in the air while being towed by a motor boat.
A man is water skiing at a lake.
riding a board doesn't always mean water skiing at a lake.
exists e1 e2 e3 x1 x2 x3 x4 x5 x6.(n_air(x4) & while(e2,e3) & Actor(e3,x5) & n_boat(x5) & of(x5,x6) & n_motor(x6) & Theme(e3,x3) & v_tow(e3) & in(e2,x4) & Actor(e2,x3) & v_jump(e2) & n_man(x3) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_board(x2) & n_man(x1))
exists p1 x1 x2.(at(p1,x2) & n_lake(x2) & exists x3 x4.((x1 = x3) & n_skiing(x3) & of(x3,x4) & n_water(x4)) & n_man(x1))