Just when sea temperatures become a bit less icy and you thought it was safe to go back in the water, something sinister starts lurking in the shallows.
Irish Water Safety has warned swimmers to beware of the weever fish, a small sandy coloured fish the venom of which can cause excruciating pain and even anaphylactic shock in its victims.
The fish lives in warm shallow water, buried in the sand with just its poisonous black dorsal fin showing. If swimmers inadvertently step on it, the spines of the fin become embedded in the flesh, leading to swelling and pain which can last for up to two weeks.
"You won't see a weever fish easily but you will know it's there if you are unfortunate enough to stand on one. The pain is usually described as excruciating," Mr John Leech chief executive of IWS said.
The weever is usually found around the low water tide line, and IWS advises avoiding swimming one hour either side of low tide.
Those who are stung should approach a lifeguard. If no lifeguard is present it is important to put the affected area into hot water to assist cleaning and break down the poison. An antihistamine may also be necessary. While anaphylactic shock can occur, the last known death caused by the weever fish was in 1927.