[citation needed] The island has an Early Christian monastery with the remains of a chapel in an enclosure and several carved slabs.

[citation needed] After being widowed in 1565, the legendary pirate queen and Irish clan leader Gráinne Mhaol (Grace O'Malley) allegedly took a shipwrecked sailor as her lover.

Seeking vengeance, O'Malley attacked Clan MacMahon's stronghold of Doona Castle in Blacksod Bay and slew her lover's killers upon Caher Island.

Caher can only be accessed reasonably safely by approaching with a small boat, such as a currach, from the east to the point marked as Portatemple on the charts.

The comment on the chart for the area, "The entire area of irregular depths up to 4 miles offshore between Clew Bay and Killary harbour 10 miles further south, breaks in bad weather" reflects the fact that even in moderate swell conditions of less than 5 metres, peaks can rise and break unexpectedly.