Talk about Shark Week.
Today brought news that a dead seal  discovered last night in Ocean Beach showed signs of having been attacked, possibly by a shark. Meanwhile, lifeguards were skeptical about a reported shark sighting  off Sunset Cliffs in Point Loma today.
Here’s a look at what you should know if you’re heading out into the water:
1. Shark attacks are exceedingly rare here.
There have only been two or three fatal shark attacks off San Diego over the past 60 years — there’s controversy over whether one was really a shark attack — and about 11 total in California: 
Join thousands of San Diegans who get the day’s news in their inboxes every morning. Get the Morning Report now .
2. Sharks are common in our waters.
Between five and 10 species of shark live within about a mile of shore in the San Diego area, said Andy Nosal, a shark researcher and graduate student at Scripps Institution of Oceanography. They include leopard, smoothhound, sevengill, swell and soupfin sharks.
“The leopard shark is the most near to shore,” Nosal said. “They certainly look fairly intimidating: they can get up to six feet long and certainly bear the general appearance of a shark. But they’re completely harmless if they’re not provoked. They’re fairly skittish, and people go snorkeling with them all the time in La Jolla.”
Other species live in the ocean beyond a mile, including makos, blue sharks and thresher sharks, he said. Great white sharks can appear both close to shore and in the deeper ocean.
Surfers, especially paddle boarders, frequently see baby great white sharks in the ocean and typically don’t report them because they’re so common, he said. Baby great white sharks just eat fish and only move on to bigger prey — such as sea lions and seals — when they’re older.
3. Most sharks are harmless. Usually.
“There are more than 400 species of sharks out there, and only maybe 20 or so are ones that we really need to worry about,” said George H. Burgess, director of the Florida Program for Shark Research. “But any species that gets to about six feet or larger can cause problems with humans because their bites — whether they mean it or not — can cause problems.”
Of all the sharks found here, great whites are the only ones that attack when unprovoked, said Nosal of Scripps Institution. It’s not clear exactly why they sometimes go after humans, Burgess said. It could be because they think they’re seals or they might believe people are an “appropriate-sized, if not strange, food item,” he said.
4. A fin in the water might not be a danger sign.
You may confuse a porpoise for a shark since they both have dorsal fins that appear above the water. But there’s a difference in how the two animals act, said B. Chris Brewster, former chief lifeguard for San Diego, via email.
“Porpoises generally move through the water in a somewhat rhythmic surfacing and submerging manner, so that their dorsal fin appears and disappears,” he said. “Sharks more typically move forward on a horizontal plane, so their dorsal fin, if visible on the surface, may stay on the surface for an extended period.”
5. You may be able to prevent or fend off an attack.
Avoid wearing bright contrasting colors, advises Ralph Collier, president of the Shark Research Committee, which tracks shark activity. “They might come up and nibble on you because they can’t figure out what you are,” he said. “Curiosity has a great deal to do with the shark coming out and looking people over.”
Jewelry is also a bad idea, he said, because it may sparkle like fish.
If you do see a shark, you might try to convince it that you’re not a delectable sea animal. “Some people suggest sticking out your arms and legs making almost a star, as no seal or sea lion would look like this,” former lifeguard chief Brewster said.
How about getting the heck out of there pronto? Collier suggested smoothly moving away from a shark, but Brewster is skeptical of that idea.
“Trying to swim away fast is probably not a winning strategy, since sharks are markedly faster swimmers than humans,” Brewster said. “Better, it seems, to face them, and if they come at you to try to strike them in the snout, eyes, whatever, in any way possible so that they sense they have made a mistake.”
And then hope the shark doesn’t feel like compounding its error.