Swimming in chlorine or salt water actually helps dreads tighten. Sitting out in the sun after that really helps them to tighten up lots, too (just remember to rinse your scalp.) If your dreads are still very new they might fall apart a bit and, especially short hair, will still need a lot of backcombing and palm rolling to stick together again. But don't worry about them falling apart too much - palm roll them when wet, then just wax them up again, once they're totally dry.