A man and his dog have had a remarkable escape after their boat lost power and took on water, forcing them to tread water in Moreton Bay for more than 11 hours overnight.

About 6am Thursday, a fisherman spotted a dog swimming in Moreton Bay, alongside other floating items including a fuel tank and tackle box.

Man and dog, reunited after an ordeal overboard in Moreton Bay. Credit:Queensland Police

The dog, a German Shepherd named Heidi, was picked up by the fisherman who took her straight back to Manly Boat Harbour to Queensland Parks and Wildlife Service.

Water police were called and began a rescue operation at 7.25am, calling in the Rescue 500 helicopter, four police vessels, a jet ski, volunteer coast guard and marine rescue.