Sei whale photo courtesy of Hannah at Marine Discovery.
Experts believe these photographs show a sei whale - the creatures rarely visit water around the UK.
Sei whales are the third largest rorqual after the blue whale and fin whale.
These photographs were taken by Penzance-based marine wildlife tour company Marine Discovery.
Hannah Jones, from Marine Discovery, said: "We're usually the last people to try and make things sound rarer than they actually are - after all simply seeing any whales off the coast of Cornwall is exciting enough. Reasons we think this whale was a Sei Whale; very visible blow, but probably not dense or tall enough for a fin whale; blow and fin seen at same time; "chin up" surface with pronounced rostrum (the "seam" running from the blowholes to the tip of the upper jaw); spots! On one of the photos, there are visible pale spots behind the fin; swathes of pale colouration on the back (though minkes do often have this as well) Feasibly large, sickle shaped fin, though you can never ID rorqual whales from the fin alone."
"So we don't think this was a juvenile fin whale as was first thought, but a possible sei whale. These are usually seen in deeper water, but rarely seen full stop. However obviously we are not utterly 100 per cent."
A sei whale can grow up to 64 feet long weighing 28 tonnes. Yet the colossal creature feasts mainly on plankton.
Sei whale photo courtesy of Hannah at Marine Discovery.
Comment: See also: Rare 45-foot sei whale dies in Virginia river
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