A fish fell from the sky and on to a man's head as he relaxed in a spa pool at Auckland's Parnell Baths on Saturday afternoon.

Photo: Supplied

Russell Hogg felt a thwack on his head then heard a large splash as though someone had "done a big belly flop" before seeing something dark sink to the bottom at the large public pool complex, near the waterfront.

He reached into the water and pulled out a large, recently deceased flounder.

"I thought, what the f***?", Mr Hogg said.

The three women he was sharing the spa pool with got a fright too, he said.

Photo: Supplied

Mr Hogg said a bird must have been flying past the spa pool with the fish in its beak when it lost its grip on its lunch.

"It must have been a big bird," Mr Hogg said, "a heron or something because a seagull couldn't hold a fish that big."

He attracted a small crowd and plenty of puzzled looks as he climbed out of the spa and walked through the busy pool complex clutching the fish.

Mr Hogg, who was visiting the pool with his family, offered the fish to his children, aged 5, 9 and 12, to hold but they declined on the grounds that it "stank too much".

Although originally from the English seaside city of Portsmouth, Mr Hogg, who now lives in New Zealand, had never heard of a bird offering such a gift to a bather before.

He knew it was good luck to be pooped on by a bird, he said, but he had no idea what having one drop a fish on his head might mean.

After taking some snaps with his surprise visitor, Mr Hogg fed the fish to some seagulls.

- RNZ