It happened around 8:30am at the Campamento Bethel campground on Red Road just off Highway 59 in San Jacinto County.
Officials said a 15-year-old was canoeing in a lake with friends when his canoe capsized.
Two others in the overturned canoe were able to get ashore, but deputies said the teen couldn't swim.
That's when a 21-year-old man jumped from another canoe into the water and tried to save him, officials said. Neither of them survived.
Both bodies were recovered from the lake and the victims were pronounced dead at the scene.
Investigators have identified the 21-year-old man as Edward Moreno.
Deputies said neither victim was wearing a life jacket. According to officials, the group had removed life jackets from both canoes and left them on the shore.