I wasn't there and the story
doesn't have many details, but if someone is in distress, whether by accident or choice, as a lifelong water sports enthusiast I would attempt a rescue or at least hope the local authorities would. The beach where this happened is the site for the Round Treasure Island Hobie regatta, has a wind and kite surfing school, and is frequented by kayakers and paddleboarders. Being inside the bay, the waves are no larger than what is found on a windy lake and the man very likely drowned in water less than eight feet deep. The beach is under a regional park district's authority and no lifeguards are stationed there, nor have I ever seen a park ranger on a boat.
Fifty-year-old Raymond Zack spent nearly an hour in the water before drowning. A crowd of about 75 people, in addition to first responders, watched from the beach in Alameda across the bay from San Francisco as Zack inched farther and farther away, sometimes glancing back, a witness told the San Jose Mercury News. "The next thing he was floating face down."
A volunteer eventually pulled Zack's lifeless body from the Bay.
Why wait for the man to be dead before trying something? More here