In 1987, Western Australia's first marine park was established just off the beach in Perth's northern suburbs.

Thirty years on, Marmion is now one of 18 marine parks managed by the Department of Parks and Wildlife, and offers a unique opportunity for snorkelling, scuba diving and fishing without having to venture too far from the CBD.

The park covers 10,500 hectares, beginning at Trigg Island, stretching along Perth's northern coastline before ending at Burns Beach.

Marine park coordinator Mel Evans told ABC Radio Perth the park's creation was somewhat trailblazing at the time for Western Australia.

"The concept of protecting certain areas of the coastline was still quite new then," she said.

"Since then we have learnt a lot ... and we have used what we have learnt in creating the rest of the parks around Western Australia."

Up close with nature just 14km from the CBD

"We are really lucky with the closeness of our park to the main centre of Perth," Ms Evans said.

"People can go out and just snorkel off the beach at Mettams Pool or in front of the Marmion aquatic club.

Mettams Pool at North Beach offers opportunities for snorkelling straight off the beach. ( Supplied: Belinda Brohman )

"They can walk straight off the beach and see some amazing things.

"It's a really fantastic ecosystem out there. We have got beautiful, shallow, clear lagoons."

Close encounters with seals, dolphins and whales

Over the years, the beaches that line the park have afforded visitors encounters with dolphins, sea lions and whales all from the shoreline.

In 2014, a two-tonne elephant seal that chose to rest up on Trigg Beach for a few days became a public sensation, attracting thousands to the beach.

A sea lion rests on the beach at Marmion Marine Park. ( Supplied: Ann Storrie, Department of Parks and Wildlife )

Beyond the beach lies a limestone reef that runs parallel to the coast that provides a home to many smaller marine life.

"We also have beautiful seagrass beds, macro algae and lots of fish around the reefs," Ms Evans said.

"If you do have a boat, there are some more complex reefs and islands offshore you can look at."

Why a marine park?

The advantage of the area being declared a marine park is the department can actively manage how it is used.

"We can select certain areas that are no-take areas, to preserve those areas for the future, but still allow for other activities to go on," Ms Evans said.

"It also highlights the significance of those ecosystems.

"Marmion is a really special section of coastline.

Just one of the fish you can see at the marine park. ( Flickr: dilettantiquity )

Undiscovered gem for many locals

On any given day, the five rangers who work in metropolitan marine parks can be found patrolling both the land and sea.

"One day a ranger might be going out and speaking to a school group about marine parks; another day they might be out on the boat checking that people are following the rules for different zones, or diving to monitor the environmental assets of the park," Ms Evans said.

And although there are 2 million visitors to the marine park every year, Ms Evans said it was still yet to be discovered by many residents.

"I think some people who are local to Perth don't know about it.