Man charged over boat ramp attack

A man has been threatened with a knife and had his boat sunk with a garden hoe in a bizarre incident at a boat ramp in Adelaide.

A 61-year-old has been charged with unlawful threats, assault and three counts of property damage after also allegedly attacking the victim's car tyres at his home.

Police say the incident at the Garden Island boat ramp occurred early on Saturday morning with the offender allegedly threatening the victim with the knife before striking and sinking the aluminium boat with the hoe.

No-one was hurt with the charged man refused bail and expected to appear in the Port Adelaide Magistrates Court on Monday.