// If the monster can submerge where it is, make it do so
            // and leave the level.
            if (monster_can_submerge(mon, grd(mon->pos())))
            {
                mon->add_ench(ENCH_SUBMERGED);
                _make_mons_leave_level(mon);
                return;
            }

            // If it's in a submersible place, make it leave the level.
            else if (mon->travel_target == MTRAV_SUBMERSIBLE
                && monster_can_submerge(mon, grd(mon->pos())))
            {
                _make_mons_leave_level(mon);
                return;
            }