Toronto Fire say one person has been sent to hospital in an afternoon which has seen multiple emergencies along the lake.
Fire crews tell NEWSTALK1010 the individual was at the dog beach behind the RC Harris Water Treatment Plant in Scarborough Sunday afternoon when they fell into the water.
CPR was performed until EMS arrived at the scene. The person was transported to hospital in East York while crews continued to perform CPR.
Further east, Toronto Fire rescued two women who became stuck on the Scarborough Bluffs.
They first received a call after 2 p.m. about the women, who had climbed up to the top and became trapped.
"Our crews - over the course of very demanding and very complex rescue that took more than two and a half hours - managed to secure about an hour ago, reached the first victim, got her secured and safely brought to the ground," Toronto Fire Chief Matthew Pegg told CP24.
"Just [after 5 p.m., we] managed to make contact with the second victim, got her secured and she's being brought to the ground as well," Pegg said.
Trenton Search and Rescue were also on the way to the scene, just in case Toronto Fire wasn't able to reach the women.
Pegg called it an extremely difficult rescue, and said the women assumed a significant amount of risk.
Meantime, the Toronto Police Marine Unit says several people on paddleboards had to be rescued from the lake at the Bluffs after they ran into trouble.
These individuals are all believed to be okay.