Holidaymakers enjoying a sea safari off the British coast got a sight for shore eyes - when they spotted this endangered 40ft WHALE.
The group watched in awe as the ultra-rare sei whale surfaced briefly off Land's End, Cornwall.
Experts say the mercurial mammals are usually only found in deep offshore waters and have only been sighted ten times before in the UK.
Hannah Jones, who runs excursion firm Marine Discovery with her partner Duncan, took a photo of the creature so that experts could verify it was indeed a sei whale.
She said: "We went out with a family who had been on a tour with us three years ago.
"It was very quiet and we were a bit worried they wouldn't have much to look at - but then Duncan shouted 'whale.'
"I wasn't sure at the time whether it was a sei whale but I went though a checklist later on and through a process of elimination I was able to identify it.
"We have contacted several professionals who, after looking at the evidence, believe it to be a sei whale also."
Named after the Norwegian word for pollock, the sei is a type of baleen whale, the third-largest member of the rorqual family after the blue whale and the fin whale.
The species can grow up to 64ft (19.5 metres) long and weigh as much as 28 tonnes.
They survive on a diet of copepods, krill, and other zooplankton and are among the fastest marine mammals, reaching speeds of up to 31mph or 27 knots.
Following large-scale commercial whaling during the late 19th and 20th centuries the sei whale is now internationally protected, with its worldwide population having dropped to 80,000.
A spokesperson for Whale and Dolphin Conservation said: "Sei whales are occasional visitors to UK waters and so sightings are rare.
"There have been only around 10 documented sightings of sei whales in UK waters and they are more likely to be spotted in colder waters off Northern Ireland."