RNLI staff were back at Three Cliffs Bay on Gower on Saturday.
Over the Easter weekend there will be lifeguards at Tenby South Beach and Whitesands in Pembrokeshire, Aberavon Beach in Port Talbot, Coney Beach and Trecco Bay in Porthcawl and Whitmore Bay on Barry Island.
Lifeguard supervisor Rob Steele urged people to go to beaches "where there are trained professionals".
At Three Cliffs Bay and Whitesands, lifeguards will be on patrol between 10:00 BST and 18:00 until 23 April.
The other beaches will be supervised from 14 - 17 April.
Mr Steele added: "Conditions can also be changeable so please bring appropriate clothing and be ready for all weathers and if you see someone in trouble in the water, don't attempt to rescue them yourself, as you could also be putting yourself in more danger."
Benny Collins, 40, died at Three Cliffs Bay in July 2015 after getting into difficulty while swimming with his nine-year-old son Harry.
His death followed those of Jason North from Macclesfield, Cheshire, the month before and Wendy Phillips of Swansea in August 2013.
Lifeguard patrols have begun at a beach where three people died in two years.