What I learned diving in the Keys this past weekend:
1) When you're entering the water, always, and especially with choppy seas, make sure your BCD has a good amount of air in it.
2) If swells are 2-3 ft and you have a tagline you are using to get to the descent line, it's a good idea to use your regulator vs. your snorkel to get over there.
3) If you decide to use your snorkel to conserve air, check the location of your reg as you swim in case you need to switch quickly to it. It's possible the reg might get swept back behind you and not be readily accessible.
3) If you are someone's buddy and you reach the descent line first, look back and make sure your buddy, who is still on the tagline, is okay before going down.
4) Dive operations should include a stethoscope and hand-pumped oxygen bag with their first aid equipment.
and
5) MOST IMPORTANTLY, DON'T PANIC when something goes wrong, try to remain calm. Staying calm increases the chance you will think rationally, assess the situation clearly, and make the right decision.