Hundreds of people have turned out at a Perth beach on Saturday afternoon to pay tribute to brothers Jake and Callum Robinson, who were killed while on a surfing trip in Mexico.

West Australian surfers, surf-lifesavers and ocean paddlers joined a "paddle-out" at Sorrento beach in Perth's north-west.

They headed out into the ocean on boats and boards and formed a circle before raising their oars in the air.

The event was put together by the Sorrento Surf Lifesaving Club, Surf Lifesaving WA, Surfing WA and the Indian Ocean Paddlers.

It took place a week after an emotional memorial service at Sacred Heart College in Sorrento, the suburb where the boys graduated from school.

Jake and Callum Robinson, aged 31 and 33, were surfing and camping in Northern Mexico when they were shot dead, along with their American friend Carter Rhoad, 30.

They had been travelling the Baja California coastline.

The disappearance sparked a frantic manhunt that made international headlines, before they were found at the bottom of a well near their camp, with local police alleging they had been shot dead after resisting the theft of their car.

The nature of the killings in a known drug trafficking area led to major questions as to whether Mexico's notorious cartels were involved, with authorities investigating the possibility.

Mexican national Jesús Gerardo, also known as "El Kekas", is the only person charged to date over the disappearance of the men.

Prosecutors allege that he discovered the three men and was motivated by a desire to steal from them.

He's accused of murdering each of them with a single gunshot to the head, before moving their bodies six or seven kilometres to dispose of them in a well.

Prosecutors say he torched the campsite, seemingly in an attempt to cover his tracks.

It's alleged Gerardo's then-girlfriend Ari Gisell told authorities her partner admitted to killing the three men.

The case has sparked calls for improved safety at Mexico's beaches, with several memorial paddle-outs also held there.