A London, Ont., lawyer was forced to cut short his marathon swim across Lake Ontario Saturday, evening about a mile (1.6 kilometres) from shore.

Greg Willoughby began the swim in an effort to raise awareness about mental health, but his Twitter page showed that his swim was aborted Saturday night.

"Swim aborted 1 mile from shore. Greg was physically unable to keep himself afloat. He boarded a police zodiac and taken to the Police Marine," the tweet said.

Willoughby began his journey Friday evening near Niagara-on-the-Lake and was expected to reach Marilyn Bell Park in Toronto by 9 p.m. Saturday.

At about 4 p.m., Willoughby's team tweeted: "Arrival time now estimated to be 9 p.m. Greg not giving up and holding a 2.5 km/hr pace. Toronto skyline getting bigger."

Willoughby, who hoped to complete the 51-kilometre swim in about 18 hours, had said the trek represented more than just a physical journey for him.

The 41-year-old immigration lawyer aimed to raise funds for St. Joseph's Regional Mental Health Care in London.

"People can talk about cancer, they can talk about heart conditions but when they talk about mental health conditions, people just don't want to talk about it," Willoughby told CTV Toronto.

His goal was to raise $25,000. Reports suggest Willoughby has so far raised half of that.