The Hawaiian surfer Garrett McNamara is said to have broken his own world record for the largest wave surfed when he caught a wave reported to be around 100ft off the coast of Nazaré, Portugal.

If the claims are verified, it will mean that McNamara, who was born in Pittsfield, Massachusetts but whose family moved to Hawaii's North Shore when he was aged 11, has beaten his previous record, which was also set at Nazaré.

When McNamara set that record in 2011, he was accompanied by fellow big-wave surfers Andrew Cotton and Alastair Mennie and at the time Mennie said that the conditions were "perfect" for McNamara whom he described as "inspiring".

"Everything was perfect, the weather, the waves," Mennie said. "Cotty and I surfed two big waves of about 60ft and then, when Garrett was ready came a canyon wave of over 90ft. The jet ski was the best place to see him riding the biggest wave I've ever seen. It was amazing. Most people would be scared but Garrett was controlling everything in the critical part of the wave. It was an inspiring ride by an inspiring surfer."

Speaking to the Observer in 2011 after his record-setting 90ft ride, McNamara explained: "We'd been invited by the government of Portugal to Nazaré to investigate it for a big wave competition. There is an underwater canyon 1,000ft deep that runs from the ocean right up to the cliffs. It's like a funnel. At its ocean end it's three miles wide but narrows as it gets closer to the shore and when there is a big swell it acts like an amplifier.

"The harbour where the jetskis are kept is about five minutes' ride away. I can see it from my hotel window. You go out and it can be almost flat as you leave and ride along the coast. You start seeing the waves after about half a mile when you pass some rocks and turn a point. Then you are in the break. It's unique. The waves break into cliffs 300ft in height. You can't contemplate coming off because it would kill you."