People sitting in a vehicle.
There are people sitting on a boat.
Vehicle can mean many different things from cars to truck to trains. There is no way to infer that the use of the word vehicle here means that they are sitting on a boat.
exists e1 x1 x2 x3.(a_topic(x1) & in(e1,x3) & n_vehicle(x3) & Actor(e1,x2) & v_sit(e1) & (x1 = x2) & n_people(x1))
exists p1 x1 e1 x2 x3 x4.((x1 = x2) & on(e1,x4) & n_boat(x4) & Actor(e1,x3) & v_sit(e1) & (x2 = x3) & n_people(x2))