Melbourne scuba diver films stunning spider crab pyramid

Hundreds of spider crabs have gathered together to form a spectacular pyramid in waters near Melbourne.

Scuba diver PT Hirschfield, 44, filmed the formation yesterday a few metres from Blairgowrie Pier, on the Mornington Peninsula.

Ms Hirschfield dives three times a week as she battles endometrial cancer and runs a blog detailing her underwater adventures.

Spider crabs usually gather in clusters before their annual migrations to safely shed their shells and have been spotted in Port Philip Bay in recent weeks.

Ms Hirschfield told 9News.com.au she had never seen this many crabs in one pyramid and believes it could be among the largest ever filmed.

“That’s really unusual,” she said.

“When they usually come in for their pre-migration, they usually stack about five or seven high.

“I was quite excited to see that they had come in in those numbers.”

Ms Hirschfield said her joy quickly turned to concern for the crustaceans.

“I was also a little devastated because some of those crabs had been entangled in fishing wire,” she said.  

“I put my camera down for ten or 15 mins to help untangle them.”

On her website, Pink Tank Scuba, Ms Hirschfield details her diving experiences.

“I’m a wannabe underwater photographer swimming against terminal endometrial cancer one scuba dive at a time,” she writes.

“When it comes to reclaiming my health, I choose scuba over chemotherapy and radiation.”