I would think that while diving any of the sites south of town, especially in the morning when there are lots of boats out, the probability of a diver on the surface being misplaced for very long is pretty low. Worst to worst I guess you could swim to shore from many of the sites, but that might not be a great idea.
One of the DMs at Blue Angel told me a story about a buddy pair who suddenly were nowhere where he could see them on a dive on Villablanca. He looked for them but he couldn't find them. He called the dive, took the group up, and then the boat captain couldn't find them, either. Panic ensued until the dive shop radioed the boat to tell them that the "missing" divers were sitting by the pool having drinks. Seems that they decided to call the dive early, went to the surface, and swam to the BA dock.