In The Monsters of Loch Ness by Roy P. Mackal (1976 Futura London) he wrote about the investigations in Ireland. The Loch Ness investigation teams did not confine them selves just to Loch Ness but also looked at Loch Morar and a couple of loughs in Ireland. Some of the information that lead them to look at Irish loughs is detailed in the book (p37-39 in the edition cited above) and includes:
Teige O’Donovan reporting sightings going back to 1914 from Lough Abisdealy (which translated means the lake of the monster). The descriptions of the creature were that it had a small flat head , along neck and three large loops sticking out of the water. Size was estimated at 25 feet( 8 metres) and the creature was dark brown. Interestingly one of the observers said the creature swung a portion of it’s body out of the water and described it as “looking exactly like the tail end of a huge conger eel”.
Lough Fadda has been discussed on here before.
There was strange sighting at Lough Claddaghduff by a Mr. Michael Coyne in 1956 who reported seeing a creature like looked like a large eel with ten feet showing as it turned over to display it’s lighter underbelly.
There was the story of the large eel stuck in a gully between Loughs Gowlan and Derrylesa from 100 years ago, which died.
In Lough Neagh in 1956 fishermen reported their nets damaged “by a thing like a giant eel”
You may wonder how this was connected to Loch Ness. There were stories that Roy Mackal mentions(p68) from older residents of Loch Ness that claimed eels of 10 feet(3 metres) to 16 feet( 5 metres) long had been caught in the loch years ago. I also heard the same stories from an elderly fisherman in 1972. He said when the eel fishing had been at it’s peak many years ago ,very large eels had been caught . I have been unable to substantiate this but I have seen it mentioned in other books about the Loch( I believe Tim Dinsdale mentions it in his books). Eels live in the loch in large numbers but are the normal European eel who don’t normally grow to enormous sizes. There have been reports of eels with manes being seen in the loch and divers reporting eels thicker than a man's leg, but no proof has been forthcoming. The theory that the lake monsters are giant eels is not a new one but when you look at reported sightings the descriptions of many say “eel like” . Eels tend to dwell near the bottoms of lakes and would only occasionally appear on the surface, perhaps when chasing fish. The manes reported could be a frill such as some fish like the Oar Fish have and a very large eel would indeed be very thick around the middle to be almost as big as a man’s thigh.
Dale Drinnon points out on the CFZ website there could be more than one type of “monster” , some sightings could be a large eel , some a huge fish. Certainly a giant eel has more credence than a plesiosaur but could be a breed of eel from the Ice Age and hence the large size. Anything is of course conjecture but then science starts with conjecture and observation and then tries to prove or disprove a theory , which is what cryptozoologists are actively doing.
I am not so well today so apologies for any spelling errors or woolly thinking.