A brand new marine rescue vessel has been vandalised on the New South Wales mid north coast.

Authorities say vandals slashed air-filled buoyancy tubes all the way around the boat, causing $50,000 worth of damage.

It was one of four rescue vessels based at Coffs Harbour for a multi-agency training exercise this weekend.

A New South Wales Fisheries boat and the police force vessel Fearless were also targeted in the attack.