Young individuals. There were four together - didn't capture all in shot. Only about one and a half to two feet long. Shoulders of other observers on the boat left in frame for perspective.
About 5 inches across shell.
breeding adult (long orange bill, paler at tip; black cap extending onto forehead; black legs)
the one in front is a juvenile; the juvenile's bill is shorter and often paler than in the adult, and the legs can be yellow