People playing in the water with a water bike.
There's some water with people playing in it.
people playing in it is a rephrasing of people playing in the water
exists e1 x1 x2 x3 x4.(a_topic(x1) & with(e1,x4) & n_bike(x4) & of(x4,x3) & n_water(x3) & n_water(x3) & in(e1,x3) & Actor(e1,x2) & v_play(e1) & (x1 = x2) & n_people(x1))
exists e1 p1 x1 x2.(in(e1,x2) & n_thing(x2) & Actor(e1,x2) & v_play(e1) & with(p1,x2) & n_people(x2) & exists x3.((x1 = x3) & n_water(x3)))