Lifeboats and lifeguards saved the lives of more than 500 people last year, new figures from the RNLI show.
The charity said that lifeboats at Northern Ireland's 10 stations launched 234 times with its volunteer crews bringing 253 people to safety in 2020.
Lifeguards helped rescue 285 people.
During three months last summer, RNLI crews came to the aid of 189 people.
Crews saved people including swimmers, kayakers, canoeists and jet-skiers as well as motorboats, fishing and sailing vessels.
High numbers of day-trippers are expected to visit the north's beaches this summer as people remain close to home during the pandemic.
Nicola Kelly, RNLI Community Manager, said: "Our lifeboat crews have remained operational throughout the pandemic and have had to operate in a different way while wearing additional PPE including surgical masks. They have done this while launching their lifeboats to help those in trouble on the water.
"As another summer approaches, we know that our lifesavers face more challenges in keeping everyone safe, which is why we are now the ones sending out our own Mayday call and asking for help."
The RNLI has now launched its annual fundraising campaign as it prepares for a busy summer.
Supporters have been asked to join the Mayday Mile, and cover at least one mile in any way they like in order to raise vital funds.
In Belfast, the RNLI has partnered with the Maritime Belfast Trust to launch the Mayday Maritime Mile.
Throughout next month, visitors can take part in a maritime themed treasure trail which takes in landmarks including the Big Fish, Clarendon Dock, SS Nomadic, Titanic Belfast, the Great Light and Thompson Dock.
To sign up, visit RNLI.org/supportMayday
