Swimmers often worry about attacks by certain marine predators. But beware the bite of a more common animal.In the wild, is a human more likely to survive an encounter with an orca or a great white shark?— Kameryn F., Yardley, Pa.By the numbers, white sharks are a lot more dangerous to humans than orcas are. Despite the name “killer whale,” there’s only one well-documented instance of a wild orca attacking someone — Hans Kretschmer, who was bitten on the leg while surfing in California in 1972. Attacks by white sharks, although still rare, happen quite a bit more often; there are several hundred on record. So why are killer whale attacks so rare? Emma Luck, a marine-mammal researcher at the University of Alaska, told me that a big part of it is just that orcas don’t encounter humans as often. “Killer whales are found in all oceans, but they tend to be found in higher densities around cold, high-latitude regions,” she wrote in a message. “These are areas where the water is not particularly inviting for the average beachgoer!”She said the 1972 orca attack was probably a case of mistaken identity, as is the case with many shark attacks. “In an open water context, where all parties can view each other clearly, I would wager that both the shark and the killer whale are going to leave you alone,” she said.In fact, you don’t have to spend long browsing police blotters to confirm that not only are killer whale attacks rarer than shark attacks, they are also rarer than documented cases of swimmers being attacked and bitten by other humans. Granted, that’s because there are a lot more humans than orcas around, but that doesn’t change the conclusion: In the ocean, you’re more likely to be attacked and bitten by a person than by a killer whale.What’s on Your Mind?If there’s a science mystery keeping you awake at night, send it to Good Question.