The shark that killed a California surfer was probably feeling really comfortable in those waters, thanks to the recent absence of humans ... according to wildlife biologist Forrest Galante.
The Animal Planet star tells TMZ ... shark attacks are always a case of mistaken identity as they hunt for seals. Forrest says this shark probably hadn't seen a surfer there in ages ... setting the stage for the fatal mistake.
As we reported ... a 26-year-old Ben Kelly was attacked and killed by a shark while catching waves Saturday off the coast of Santa Cruz County.
A photog for KRON-TV in the Bay Area said he spotted 15 great whites swimming near shore the day of the attack, and has been seeing lots of sharks near shore recently.
Forrest says the increase in shark sightings makes sense ... because with most humans in quarantine and less folks venturing into the ocean, sharks are hunting in areas previously packed with people.