. >> reporter: david mcguire is a research scientist and shark stewards. he says the video shows something never before seen in the san francisco bay. a white shark attacking its prey. >> it's actually a sign that maybe the san francisco bay is getting a little healthier. that you have top predators coming in. >> sharks tend to follow their food. seals and sea lions are staples. mcguire says sick and starving sea lions show a need for more predators like white sharks. at krisy field no one is dipping their toes in the water thinking of sharks. >> a great white shark? i didn't know those come into the bay. that is pretty scary actually. >> i thought they stopped at the golden gate. >> they can and do. >> but that doesn't mean white sharks are looking for a snack along the bay shores. >> there are people swimming, enjoying the bay every single day without risk of shark attacks. there is much higher risk like getting hit by a boat. >> this morning we caught up with pretty educated swimmers who braved the waters of the san francisco bay. here's what they had t

. >> reporter: david mcguire of shark stewards said it's unusual to see but not unusual for a shark to eat a sea lion. >> that is their natural prey. we are not -- we are not their natural prey. 90% of humans who get bit in california survive white shark attacks. generally they bite, realize it's a mistake, and spit us out. if we can get home and patch up, we're okay and survive. that's the best thing i've ever seen in my life. >> it's exciting for once for someone to witness but a sign the bay is getting healthier when you have predations. that means the ecosystem is become more balanced. it worries me it's a sign they may goof humans. >> it would be extremely rare and we swim. we swim in san francisco bay all the time. there's never been an attack on the swimmer. the odds are much higher you're getting in an accident or falling off your bicycle or bathtub. the odds are extremely low. >>> up next, sit or stand? one school in marin county said students who stand benefit in many way. >>> want more vacation days? linkedin may be the perfect place for you to work. we'll tell you act its v

. >> david mcguire a research scientist with california academy of scientists.he says the video shows something never before seen in the san francisco bay. a white shark attacking its pray. >> it is san francisco bay. you have top predators coming in. >> sharks tend to follow their food, fields and sea lions are staples. mcguire says sick and starving sea lions coming to shore this year show a need for more predators like white sharks. >> and no one is dipping their toes in the water thinking about sharks off alkatr as island. >> in is pretty scary. >> they can't get past. we can't go past the bridge. i guess they can. >> they can, and do. >> it's jaws. >> but that doesn't mean white sharks are looking for a snack along the bay mother. >> there are people swimming, enjoying the bay every single day without risk of shark attack. there are much higher risks like getting hit by a boat especially on a day like today. >> when everybody else is looking in the water. >>> noel walker, ktvu. 4:08 is the time a new insurance products for lift drivers. the first of its kin

. >> reporter: david mcguire, director of shark stewards, a shark conservation group wants to point out the sharks pointed out by the coast guard were not clustered in one place. >> it's not a school or swarm or vicious of man eating sharks, they are preying on the normal prey which is seals and sealions. that said, you have this situation and the other one of alcatraz, in my people nervous to go into the water. if people are afraid to go into the water, this may not be the best time to go in. wait until the sharks leave the coast until later in the year. and if you are not afraid, go ahead and swim. we all have risk in our lives, use the best information and use that risk to regulate your behavior. >> reporter: joe vazquez, kpix 5. >>> 21 minutes before 5:00, bulldozers washed up at bay area love on purpose. why it's actually a good thing. >>> and what is cool about your school? email your nominations to us, coolschools@kpix.com and we may feature your school on our show. ,,,,,,,,,,,,,, coast guard teamed up yeste to free a humpback whale. the whale became tangled in net of a lobster t

>>reporter: david mcguire of the nonprofit group shark stewards says it's unusual to see but not unusual shark to eat a sea lion. >> that is their natural prey. we are not. >> we are not their natural prey 90% of humans who get bit in california survive white shark attack. they bite they realize it's a mistake. they spit us out. if we can get home get patched up we're okay. >> that's the best thing i've ever seen in my life. >> it's exciting for someone to witness but also it's a sign that the bay is getting healthier. that when you have per dayss it mean the eco ecosystem is weeking balanced. >> you and i swim in the san francisco bay all the time. there's never been an attack on a swimmer. the odds are much higher if you get hurt talk off your bicycle or your bathtub. >>reporter: joe vazquez can by, 5. >> danger of a different kinds for swimmers in foreign and southern california but it has been in southern california where lifeguards have been busy pulling people out of the water. because of what we've been warning you about all weekend those rip currents. there were more than 400 res