The dirty vehicle is caught in a flood.
The vehicle is on a boat.
If the vehicle is on a boat, it can't be caught in a flood.
exists e1 x1 x2 x3.(n_vehicle(x1) & of(x1,x2) & n_dirty(x2) & in(e1,x3) & n_flood(x3) & Theme(e1,x1) & v_catch(e1))
exists p1 x1.(n_vehicle(x1) & exists x2.(on(x1,x2) & n_boat(x2)))