Two people in the water while two other people are jumping out of the water.
The people are playing in and out of the water.
Two people and two other people can be commonly referred to as the people.
(x)
exists e1 e2 s1 x1 x2.(n_water(x2) & n_people(x1) & of(e2,x2) & r_out(e2) & Actor(e2,x1) & v_play(e2) & a_in(s1) & Manner(e1,s1) & Actor(e1,x1) & v_play(e1))