Three people in various stages of swimming strokes race along colorful lane markers.
The people are doing the back stroke.
Not all swimming strokes are back strokes.
exists s1 s2 x1 x2 x3 x4 x5 x6 x7.(a_topic(x1) & in(x1,x2) & of(x2,x3) & along(x3,x6) & n_marker(x6) & of(x6,x7) & n_lane(x7) & a_colorful(s2) & Theme(s2,x6) & n_race(x3) & of(x3,x5) & n_stroke(x5) & of(x3,x4) & n_swimming(x4) & n_stage(x2) & a_various(s1) & Theme(s1,x2) & n_people(x1) & card_eq_3(x1))
exists e1 s1 x1 x2.(n_stroke(x2) & a_back(s1) & Theme(s1,x2) & n_people(x1) & Theme(e1,x2) & Actor(e1,x1) & v_do(e1))