Three brothers were searching the Wellington coastline for somewhere to dive this morning when they came across a monster squid washed up on a beach.

Daniel, Jack and Matthew Aplin were driving along the track near Red Rocks on Wellington's south coast when they spotted it.

"My brother said 'what's that over there?' and pointed it out," Daniel Aplin said. "It was right next to the track so we pulled over and we were like: 'It's a big squid'."

Diver Jack Aplin with a giant squid that washed up on Wellington's south coast. Photo / Supplied

They took photos of the squid which dwarfed Aplin's two brothers who are "big dudes".

"After we went for a dive we went back to it and got a tape measure out and it measured 4.2 metres long," he told the Herald.

A spokesman from the Department of Conservation said it was most likely a giant squid, not a colossal squid like the one at Te Papa.

A giant squid has been found washed up on Wellingtons south coast pictured with diver Matthew Aplin Supplied OCEAN HUNTER Spearfishing & Freediving Specialists 26 August 2018

Posting to the Ocean Hunter Spearfishing and Freediving Specialists Facebook page, diving pundits from around the country expressed shock at the discovery.

"That's a whole heap of calamari," one said. "People worry about sharks. Bugger seeing that in the water," said another.

Aplin and his brothers had seen a few sharks while diving in the area but had never seen a massive squid before.

He said it appeared to have shrunk while they went away diving and didn't appear to have any signs that it was attacked by another animal.

"It was pretty clean, nothing major on it. There was a scratch on the top of its head but smaller than a lighter, tiny, wouldn't think that's what killed it," he said.

The brothers weren't sure who to call and eventually decided to contact a friend from Niwa, who organised for the squid to be collected, Aplin said.

For anyone wondering, the squid brought the trio good luck, ending the day with a bagful of paua and butterfish.