// If the monster isn't travelling toward an exit or a trap,
            // make it start doing so.

            // If the monster isn't travelling toward someplace from
            // which it can leave the level, make it start doing so.

            // If it's on a stair, next to a trap, or can submerge where
            // it is, make it leave the level.

            // If the monster is leaving the level via a stair or
            // submersion, and has reached its goal, handle it here.

                    || mon->travel_target == MTRAV_SUBMERSIBLE
                        && monster_can_submerge(mon, grd(mon->pos()))))

                    || mon->travel_target == MTRAV_SUBMERSIBLE))

                if (mon->travel_target == MTRAV_SUBMERSIBLE)
                    mon->add_ench(ENCH_SUBMERGED);

            // If the monster is about to step on a trap to leave the
            // level, handle it.

            // If the monster is leaving the level via a trap, and is
            // about to reach its goal, handle it here.