A schoolboy is being hailed as a hero after taking swift action to help save himself and his family as their boat capsized off the west Wales coast.

David Matthews, 15, from Ammanford, Carmarthenshire, was in the boat with three other members of the Matthews family - John, 65, Andrew, 59, and Meurig, 43 - when the drama began near Tenby, Pembrokeshire.

These men are incredibly lucky to have survived this ordeal

Nigel Porter, Coastguard

The crew were left powerless when the 15ft-long Nonina III was struck by a wave, causing it to fill with water and capsize as darkness fell on Thursday.

None of those on board had been wearing life jackets, and their emergency distress flares were in a submerged locker under the overturned vessel.

But quick-thinking David managed to dive under the gunwhale of the boat to retrieve them and fire them off, before swimming back to shore to call for help.

The first of the red flares failed, but the final one was spotted by the off-duty policeman, who was looking out to sea at the time.

"Fortunate" : Andrew Matthews

Coastguards said they were just lucky that the officer had bought a pair of binoculars on the same day.

The Milford Haven Coastguard was alerted and all four were rescued from the water and taken to Withybush Hospital in Haverfordwest.

They were treated for hypothermia, but have since been released.

One of the men, who had previously broken his arm, and still had it in a sling, was also treated after swallowing motor oil from the boat.

Rescuers alerted

Meurig Matthews - who was trying to swim to the shore one mile away - was picked up first.

He alerted his rescuers to the plight of the others still in the water.

Nigel Porter, Milford Haven Coastguard watch manager said: "These men are incredibly lucky to have survived this ordeal. Their story could so easily have been far more tragic.

"Meurig, they decided, was the best swimmer and he swam for shore - but I doubt very much whether he would have made it.

Many vessels get into trouble off the Tenby coast

"The teenage boy David was very brave and dived underneath the upturned boat to get the flares.

"It was getting dark, they had about another 15 to 20 minutes for someone to spot them.

"Without the red flare they would not have been spotted.

"It is difficult to say how much longer they could have survived in the water.

"They were all suffering from hypothermia, they had about another hour or two at most."

Andrew Matthews and his wife Ann - David's grandparents - were counting their good fortune on Friday.

"We were really fortunate, really," Mr Matthews said.

"I thought the boat was going down, and we didn't know if they had seen the flares."

His wife added : "I could have lost them all - my husband, my grandson, my brother-in-law, and my nephew. They've all been very lucky."