People are on a roller coaster next to water.
People on a roller coaster.
Both subjects are on a roller coaster
exists p1 x1.(exists x2 x3 x4 x5.(on(x1,x2) & to(x4,x5) & n_water(x5) & next(x2,x4) & n_thing(x4) & n_coaster(x2) & of(x2,x3) & n_roller(x3)) & n_people(x1))
exists x1 x2 x3.(a_topic(x1) & on(x1,x2) & n_coaster(x2) & of(x2,x3) & n_roller(x3) & n_people(x1))