An investigation is underway into a fire which destroyed three boats at a marina at Toronto this morning.

About 1.45am today (Sunday 10 January 2016), a man and woman sleeping on a boat, moored at the Wharf Street marina were woken by a loud noise.

They went to look and saw cruiser moored nearby well-alight; they swam to shore and alerted emergency services.

Fire & Rescue NSW fire-fighters contained the blaze with three cruisers destroyed. The vessels have an estimated value of $200,000. Several other boats were damaged.

A crime scene has been established and an investigation is now underway by Lake Macquarie detectives, assisted by Marine Area Command.

At this time the cause of the fire is unknown.