Visitors to a U.S. aquarium got a bit of a surprise the other day -- when a deer took an impromptu dip in the seal tank.

Staff at Maritime Aquarium in Norwalk were feeding the seals when they noticed an animal swimming around which didn't belong.

It was a small deer which had swim across a river to get to the aquarium and then hopped into the seal display -- luckily the seals were safely in the inside part of the display at the time.

A 30-minute rescue mission was launched and after attempts to net the deer failed, they placed a ramp in the water so the deer could get out himself, which he did.