Small shiny blue black beetle like insect about 40 of which were gathered in weedy water.They were 7-8mm long.
No interactions present.
There are 10 species of Whirligig beetles in Ireland - they are pretty difficult to tell apart without a specimen. That said, the common whirligig Gyrinus substriatus, is as common as all the others put together - so its most likely this! There is an article and key in a recent British Wildlife magazine (20 - p28-35).
Lat/Lng: 52.5, -7.8
OS grid ref: SF0815