It's long been argued that when people report seeing sea serpents, they might actually be seeing floating logs, strange waves, or shadows on the water, and mistaking these things for sea serpents. Now Dr. Charles Paxton has come up with an interesting extension of this theory. He argues that people might also be misidentifying whale penises as sea serpents. He presents this theory in the current issue of the Archives of Natural History. As an example he uses the case of an eighteenth-century missionary named Hans Egede who reported a sighting of a sea serpent, and drew a picture of the creature. Paxton demonstrates that Egede's picture closely resembles what a whale's aroused penis rising from the water might look like. The abstract of Paxton's paper is as follows:

A re-evaluation of the “most dreadful monster” originally described by the “Apostle of Greenland” Hans Egede in 1741 suggests that the missionary’s son Poul probably saw an unfamiliar cetacean. The species seen was likely to have been a humpback whale (Megaptera novaeangliae), a North Atlantic right whale (Eubalaena glacialis) or one of the last remaining Atlantic grey whales (Eschrichtius robustus) either without flukes or possibly a male in a state of arousal.

So if Egede mistook a whale penis for a sea serpent, it's logical to assume others might also have done so. This theory has the ring of truth to it.