On the beaches of Standhill and Rosses Point, I was warned many times not to go swimming as the current is VERY strong. I was first warned by the taxi driver who was driving me and my travel buddy (VT Username J.I.M) to the campsite we was headed. Then we was warned by the Campsite owner, then a couple who were staying in a nearby tent. And then our final warning to not go swimming was when we went to the other campsite at the other peninsula.
Though they said it was a great place to surf...
Sligo Town rests at the coastline of Northwest Ireland, and therefore it can have a very beautiful sea, particularly at sunset. However, as tempting as it is, swimming is not recommended at all. Several locals warned Wayne and I not to go swimming in the sea, as the Atlantic current is very strong and could easily pull you away from land.
However, I believe it might be okay to swim in certain areas; just make sure you ask first.