THE Celtic Sea revealed its secret giants to a Pembrokeshire-based marine conservation group last week.
Sea Trust teamed up with Stena Line to carry out a ferry-based survey between Rosslare in Ireland to Cherbourg in France.
On the route marine observers came across a large group of feeding fin whales.
“We were incredibly lucky” said Cliff Benson, Sea Trust director.
“The weather on the outward crossing had not been so favourable and as we left Cherbourg the previous night it seemed to be worsening.
“We got onto the bridge at dawn, starting the second leg of our survey as we passed Land’s End. The sea had calmed down and visibility had really improved.”
Hannah Harries, Sea Trust science officer, said: “First we saw the massive blows and then a few minutes later a huge fin whale surfaced just ahead of us.
“I had worked off the Great Barrier Reef and spent many hours watching dolphins in the Irish Sea but this was my first encounter with the second largest animal that has ever lived on earth.
“It was so exciting. We positively identified at least 12 different individuals but there were probably a lot more from all the blows we could see.”
After the fin whale sightings, the group came across a couple of minke whales and a large pod of common dolphins near the Smalls Lighthouse.
Cliff added: “The cetacean research is all about putting together small pieces of information like a jigsaw puzzle and trying to create a real picture of where they are, what they are doing and how we can best protect them.”