Forget snapper and flathead — an echidna has claimed the title of catch of the day after it was plucked from the waters halfway between mainland Queensland and Bribie Island.

Marlyn Rasmussen was out fishing with her husband, aunt and uncle on Pumicestone Passage on Wednesday afternoon when she came across the prickly swimmer about 200 metres off the mainland.

"We saw something, didn't realise what it was until she came closer and she literally swam straight to the back of the boat as if to say 'help me'," Ms Rasmussen said.

With the help of a landing net they brought the echidna onboard.

"She went into defensive mode, curled up into a ball. There was a big black rubbish bin on the boat so we put him in there to keep him safe till we got back. She seemed OK," Ms Rasmussen said.

"I thought for an animal to come straight up to the boat, it was as though he was looking for help."

The Rasmussens left the echidna with Bribie Island Boat Charters, who took it to Australia Zoo Wildlife Hospital for a check-up.

An Australia Zoo spokeswoman said the echidna has been given the all-clear and released back into the wild.

"She came in for an x-ray and she was fine. She had no fluid in her lungs," the spokeswoman said.

"The wildlife rescuer who brought her in also released her back into bushland near where she was found."

Queensland Museum's mammals and birds senior curator Dr Paul Oliver said despite appearances, echidnas are known to be good swimmers.

"Indeed the latest fossil evidence suggested they descended from aquatic platypus like ancestors," Dr Oliver said.

The echidna's escapade was reminiscent of a koala caught on camera doggy-paddling across Kangaroo Island's Harriet River earlier this year.