 Ideally, knowing where you are. Believe it or not, we get many calls, but people have no idea where they are. And the dispatchers do a great job of piecing it together by description. So my advice would be if you're going to go somewhere swimming, know where you are, bring a fully charged cell phone, and if something happens, the sooner you call 911 and one of our dive teams can get underway, the greater the chance there is to recover them within an hour, in which case there is a chance of resuscitation.