two surfers are riding waves in open water.
Two surfers are practicing for their next competition.
Just because surfers are on the waves doesn't imply they are practicing. Just because surfers are on the waves doesn't imply they are readying for a competition.
exists e1 s1 x1 x2 x3.(in(e1,x3) & n_water(x3) & a_open(s1) & Theme(s1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_wave(x2) & n_surfer(x1) & card_eq_2(x1))
exists e1 s1 x1 x2.(for(e1,x2) & n_competition(x2) & a_next(s1) & Theme(s1,x2) & of(x2,x1) & n_thing(x1) & Actor(e1,x1) & v_practice(e1) & n_surfer(x1) & card_eq_2(x1))