According to a Greek newspaper, his girlfriend was filming him from the shore during the incident.
The Foreign Office stated that it was providing assistance to his family and communicating with local authorities.
It is currently unknown whether Mr. Seddon was directly impacted.
The Port Authority of Rhodes was unable to provide additional information due to the “active” nature of the investigation.
The Press Association reported that the Greek newspaper Rodiaki reported that the 26-year-old fell into the water after being struck by lightning near the water shortly before 13:30 local time (09:30 BST) on Tuesday.
The newspaper reported that a passerby, identified as a local footballer, pulled him to shore. And he was subsequently transported to a local hospital, where he was pronounced deceased.