Heuvelmans imagined that there were three living archaic whales: Super-Otters in the Arctic, Many-Humped* in temperate waters, and Many-Finned in the tropics. The Many-Humped was portrayed as a close relative of Basilosaurus but equipped with hydrostatic humps and osteoderms. Most of these could be creatively interpreted standing waves or groups of animals; the Princess is really the odd man out and could be a flat-headed tooth whale such as a Rough-Toothed Dolphin or mesoplodont. Heuvelmans rejected the Basking Shark explanation for the Hilary sighting based on a more detailed description.
* Bestowed the name Plurigibbosus novae-angliae… which should be ‘novaeangliae’.
Heuvelmans, B. (1968) In the Wake of the Sea-Serpents.