Richard Guest, 74, along with another person, went into the sea in Tywyn on 4 July but had to be recovered by coastguards.
Coroner Peter Brunton concluded he died as a result of misadventure.
Speaking after the inquest, Mr Guest's widow Margaret said: "He was a big man, a strong swimmer who just wanted to help."
Originally from Bethel near Caernarfon, the couple were on holiday from their home in Walsall, West Midlands, when he died.
The inquest heard Mr Guest's heart was "profoundly enlarged" and almost twice the weight of a healthy heart but that he was unaware of his condition.
The pathologist said a "cardiac event" could have been caused by Mr Guest's exertion in the water but the cause of death was given as drowning.
Mrs Guest added: "Even if he had known he had a heart condition I think he would have still gone into the sea. That's the kind of man he was - he was always looking out for other people."
A grandfather drowned while trying to rescue two teenage girls from the sea in Gwynedd, an inquest has heard.