By Crystal Chung @crystalkchung
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Californian photographer Phillip Crolla captured beautiful images showing schools of fish weaving between the network of beams.
Also visible are various brightly coloured anemones that have attached themselves to the oil rig's underwater legs.
Phillip took dives around three different oil rigs located eight miles off the shore of Long Beach, California, named 'Eureka', 'Ellen' and 'Elly'.
The underwater adventurer said: “What you see in the photos are giant steel beams, a lattice of struts from which the oil rig is built.
"Below the surface of the ocean, these beams are covered with life, invertebrates of many kinds that attach to the beams and grow.”
Another image shows a friendly sea lion as it gets up close and personal with the camera.
Phillip said: “Californian sea lions often haul out onto the beam above water to rest and can be found swimming among the underwater beams foraging for food or playing with scuba divers.”
The 52-year-old is no stranger to the ocean and has travelled throughout the world photographing life underwater from Alaska and Antarctica to the Galapagos and Central and South America.
He said: “I suppose for some people it might be disorienting. Huge metal struts are seen in all directions: up, down, left, right.
"But the beams are covered with life. Invertebrates like mollusks, starfish, crabs, and millions of colourful small anemones.
“After I got familiar with how the oil rig beams are situated underwater, I was able to relax, hang out and watch the passing fish and sea lions, and shoot photos of the invertebrate life on the rig’s beam.
"It was a lot of fun and I will definitely return to do it again.”