The lifeboat crew were paged at 7.10am after members of the public raised concerns about a swimmer in the water.
A D class lifeboat was launched and quickly located the individual underneath Penarth Pier.
In an update shared after the incident, Penarth RNLI said: “Our crew were paged at 07.10 this morning after members of the public reported a swimmer in difficulty.
“The D class was launched and immediately located the swimmer who was underneath the pier.
“The swimmer confirmed he did not require assistance and after our volunteers were able to stand down and return to station.
“Thanks to our colleagues at HM Coastguard – Penarth for also responding.”
Although no rescue was ultimately required, the RNLI has used the incident to remind people to take precautions when swimming in the sea.
The charity added: “We’d like to encourage anyone sea swimming to use a swim float for visibility. Wetsuits provide extra buoyancy and if you find yourself in difficulty remember to Float To Live.”
The RNLI’s Float to Live advice encourages anyone who gets into difficulty in the water to float on their back, relax and control their breathing until they can call for help or reach safety.
