The organisers of a triathlon in which a man died said he got into difficulty while swimming.
All or Nothing Events said a safety crew was deployed to help the 43-year-old competitor during the SWYD Sprint Triathlon on Barry Island on Sunday.
Emergency services were called to the triathlon on Whitmore Beach just after 07:30 BST.
Ambulance crews and the coastguard tried to save the man, who it is believed had suffered a cardiac arrest.
The organisers said: "We take the safety of competitors extremely seriously and adhere to strict guidelines in order to provide and a safe and enjoyable experience.
"For a tragedy like this to have happened is devastating to everyone concerned, including all of the other competitors who took part.
"We would like to pass on our deepest sympathy to the family and friends of the competitor, and would like to thank the emergency services for their efforts."
The triathlon comprised a 750m sea swim followed by a 20km bike ride and 5km run.