Dawn can be calm or it can be rough. Galion and Dawn boast the best reefs on the island, but require a fairly calm day for their exploration. Easy access from one of the resorts on the beach otherwise not so easy access - all beaches are public.
We didn't find many people on Dawn Beach except down on near Westin area. The Villas and Westin seem to completely shut out access. The reef there is very nice; but Bobcat is right, it requires a less windy day. When we were there, the wind ranged from very high to medium high. My son and I float well so we snorkeled on the medium high days and really enjoyed it. Not for inexperienced snorkelers. Kids loved the small waves that crash. Great beach.