Devenish Island sits on Lower Lough Erne in Co Fermanagh.
The historic strip - which measures just over a mile long - is a popular beauty spot for tourists and locals.
Visitors usually catch the ferry at Trory Point, a few miles from Enniskillen town centre, and make the 15-minute journey to one of the two jetties on the island.
Yesterday's tragedy is not the first at Devenish.
In 2007 Declan Swift (47) and Martin Steele (48) fell into the water from their fishing boat.
The two Enniskillen men had been making their first trip in a boat bought the day before they drowned.
Last year Caroline Somerville, a librarian at Belfast Bible College, suffered horrific injuries after she was attacked by a cow on Devenish.
The mother-of-three had been visiting the island with family members when the freak incident occurred.
Devenish, which is owned by the Kilravock Christian Trust, is said to contain one of the finest monastic sites in Northern Ireland.
It was founded in the sixth century by Saint Molaise, who established a small monastery on a pilgrim route to Croagh Patrick in Co Mayo.
There are ruins from different time periods on the site, including a famous round tower that dates back to the 12th century.