James Cameron is allegedly being sued for $300million by a Florida man who claims the Titanic director stole one of his stories to create Leo DiCaprio's character in the movie.

Stephen Cummings is said to be adamant the role of Jack Dawson was taken from a nearly 30-year-old tale.

Court documents appear to show the complainant is arguing Cameron got the idea from a conversation he overheard back in 1988 about events that took place in Brevard County when the former yacht master was talking to his friends.

Movie director James Cameron talks to reporters at an event to promote the New Zealand film industry in 2015

Leonardo DiCaprio pictured as Jack Dawson with Kate Winslet as Rose DeWitt Bukater, in a scene from the film directed by James Cameron

The Titanic sinks in the movie - the fourth most profitable to hit the silver screen in history

Not only is Cummings saying the tragic case of happy-go-lucky Dawson is based on his stories, but he claims the story of how the doomed ship sank was stolen from him too, according to US site.

He thinks Cameron took this idea from another story he told friends about two of his relatives he says were on the ship.

In that tale, the wife survived and the husband drowned.

It's unlikely to be a unique story, given 1,517 people died on April 15, 1912.

As well as the $300million, Cummings wants one percent in royalties, according to TMZ.

Cameron's Titanic, which he created for $200million, is the fourth most profitable movie of all time, with box office profits of $2.5billion.

But even if this is proven right, there is no copyright law relating to an idea, and Cameron is unlikely to have to hand over any money.

MailOnline contacted the director for comment, but he did not immediately respond.