It is critical to let somone other than than the diving group know where you are, when you you will be diving, when you will return , and any other important information. Family, friends, shore support, local beach guards or marina personnel, or someone can be easlily found and notified. When I take a party diving from shore, even just for fun, we always have a "shore guy" along, too. If a boat excursion, the marina knows we are out and someone always stays on the boat. Its just common sense and it is a big safety factor.
DivemasterDennis