From a newspaper account of an island delivery in 1971:
"Mrs. Dorothy Williams of Ocracoke had what could be called a very rough delivery. A 30-foot Coast Guard boat, which had picked up Mrs. Williams to take her to Hatteras to have her baby, was immobilized in heavy seas after running onto shoals. An open 17-footer tried but was unable to get along side the boat due to heavy seas and wind. Finally, an amphibious vehicle of he Coast guard rolled aboard [I think they meant "alongside"] the Coast Guard boat, bringing Dr. Dan Burroughs who delivered the baby in knee-deep water."
US Coast Guard 30-footer:
US Coast Guard Amphibious "Duck" Boat (all-wheel drive utility vehicle with dual rear axles):