A sailboat  and a humpback whale nearly collided in San Francisco Bay over the weekend, and the incident, which was caught on video, is prompting renewed calls for boater safety.

The humpbacks are back, feeding on anchovies in the Bay as they were previously seen doing in the spring — they now appear to be on their southward migration from Alaska, having stopped off around SF in May, on their way north, along with a bunch of gray whales. And on Saturday, September 7, a near-miss incident was caught on camera and shared by San Francisco Whale Tours, with a sailboat that had to quickly veer out of the way of a surfacing humpback. The whale appears to see the boat at the last minute and dives underneath its keel.

As KPIX reports, Michael Pierson, a naturalist with SF Whale Tours who was aboard the Kitty Kat, the boat from which the video was shot, says that the sailboat was operating irresponsibly while other boats in the area which had seen the whale were keeping a proper distance.

The Marine Mammal Protection Act requires boats to give a 300-foot buffer to whales, and this boat clearly did not do that, coming within about 10 feet of the creature.

The presence of whales in the Bay may be surprising at this time of year, but the simultaneous presence of so many boats and ships has already led to other unfortunate incidents. Less than a week earlier, whale watchers witnessed a ship strike and kill a humpback in the Bay near Alcatraz Island.

And NBC Bay Area's Mark Matthews posted a photo on September 2 of a speedboat that was doing doughnuts around a surfacing whale.

As Steve Jones from the Center for Biological Diversity tells KPIX, "It’s a beautiful thing to see whales here in the San Francisco Bay. I think that’s something we all want to see. But there’s a lot of boat traffic here. We need to be very careful." He adds that in the case of the sailboat above, it's not exactly clear whether the sailor could have done better to avoid the whale, "but certainly, federal law calls for boaters and individuals to keep their distance from marine mammals."

A spate of over a dozen dead gray whales showing up on the shores around San Francisco prompted wide concern among marine biologists this past spring. The reasons for their deaths were primarily malnutrition, though ship strikes were responsible for several of them.

Previously: It's Officially Whale-Spotting Season In San Francisco Bay