Duty skipper Glenn McAdam said there was only one diver, they didn't put a buoy into the water to indicate where the diver had submerged, and the woman was only equipped with a handheld radio that she didn't know how to use.
It would have been like trying to find a "needle in a haystack" had they needed to do an air search, he said.
In light of the incident, he wanted to encourage women to sign up to the Hawke's Bay Coastguard's new Suddenly in Charge course, designed to teach women the basic skills needed if they find themselves in charge of a vessel at sea due to unexpected circumstances.