Five people have been rescued from the cold ocean after the hull of their boat split and it overturned about 20km off the coast of Mindarie this morning.

Those onboard were able to activate an EPIRB and make a mayday call to police before they went into the water just before 9am.

The rescue helicopter found the group in the ocean clinging to the hull of the stricken vessel. The police helicopter hovered over them until a Whitfords Volunteer Sea Rescue boat arrived to pull them to safety about 9.35am.

The group told rescuers the hull of the catamaran began splitting and the boat took on water. It then rolled and began sinking.

Rescuers are bringing the five people to shore at Mindarie and towing their boat in.

Water Police and sea rescue groups said it was the latest in a series of rescues over the weekend and it was unusual to have so many emergencies during winter.

Three men were pulled from the water yesterday afternoon after their fishing boat overturned near Garden Island.

Water Police Sgt Michael Wear urged skippers to carefully check weather conditions before heading out. “Check not just the wind but the sea and swell,” he said.

He said cases water police were involved with over the weekend, which included five separate rescues around WA, showed the importance of having safety equipment such as EPIRBs onboard.

“Lives were saved this weekend because the boats all had EPIRBs and searchers could be directed straight to the stricken vessels,” he said.

“Boaties need to have the correct safety equipment, making sure EPIRBs are registered and ensure they let people know where they are going.”

Fremantle Volunteer Sea Rescue Group operations officer Frank Pisani said the high level of boating activity had prompted rescue groups to man more vessels than they would normally in winter.

He also urged boat owners to ensure they had working radios and log in with their local sea rescue group before heading out.