SAN DIEGO -- A man on a jet ski crashed into another rider Saturday on Mission Bay and then sped off, leaving a woman injured, 10News reported.

It happened around 2:30 p.m. near the DeAnza Cove launch ramp, said a dispatcher with the Fire Department.

The woman gave police a description of the man, who left her alone in the water with possible broken bones, said San Diego Lifeguard Nick Lerma.

Police staked out nearby launch ramps in an effort to find the man.

There have been "higher than usual injuries" on the waterways this year, said officer Larry Hesselgesser of the San Diego Police Department.

The waters and beach have been filled with crowds of people, including boaters who don't know how to use their craft safely, said Lerma.

"Don't just get on your boat and go as fast as you can," he said.

Hesselgesser said Mission Bay has had three propeller injuries this year, including a fatality at Campland.

In addition to the three propeller accidents near Ski Beach, there have been accidents involving craft along the bay, including one in which three girls were hit by a private watercraft last weekend, police said.

"Be aware of your surroundings. Riding at a high rate of speed can do a lot of damage," said Lerma.

Lerma also cautioned boat owners to watch their crew, because if a major crime would occur onboard, the owner would be responsible, he said.