People wearing swimming suits playing in the water.
They are wearing swim suit playing in the water while having a barbeque
Not every person playing in the the water is at the place while having a barbeque. There is no mention of food at all and for all we know they could only be there to swim or play in the water.
exists e2 e1 x1 x2 x3 x4 x5 x6.(n_water(x6) & a_topic(x1) & Theme(e2,x3) & Actor(e2,x2) & v_wear(e2) & in(e1,x6) & Actor(e1,x5) & v_play(e1) & (x3 = x5) & n_suit(x3) & of(x3,x4) & n_swimming(x4) & (x1 = x2) & n_people(x1))
exists e3 e2 e1 x1 x2 x3 x4 x5.(n_water(x4) & Theme(e3,x2) & Actor(e3,x1) & v_wear(e3) & while(e1,e2) & Theme(e2,x5) & Actor(e2,x3) & v_have(e2) & n_barbeque(x5) & in(e1,x4) & Actor(e1,x3) & v_play(e1) & (x2 = x3) & n_suit(x2) & of(x2,x1) & n_swim(x1) & n_thing(x1))