Martin Kenny, who rehabilitates and hooves horses for a living in Elk Neck State Park, was surprised by his find and noticed the phallic rock also had a hole going through the um, shaft.

Kenny told Metro.co.uk: 'I just looked down and there it was. Thank God the customer I was with didn't see it, she was a bit of a loose woman - she might have expected to have gotten invited inside!'

A close-up of the hole in the base of the rock. (pic: Matin Kenny)

Some have postulated that the rock is in fact a stalactite but Kenny soon rubbished these claims as the rock is not made of limestone.

The almost drill hole-like recess in the centre is also unexplained.

Kenny, who lives at the tip of a peninsula, believes the rock could be part of a sculpture that fell off while being moved from a boat.

He has contacted the Smithsonian Museum about the find but has so far had no response.