YOU SAID IT: Tin can diplomacy

Amid signs that the North Atlantic’s great white shark population is growing, popular Cape Cod beaches are using technology to warn swimmers and surfers when it’s time to get out of the water. And while Nova Scotia is only 265 nautical miles away from Boston, as the shark swims, beachgoers in Canada’s ocean playground have no such protections. “We are able to detect tagged sharks — sharks that are carrying acoustic transmitters — and those transmitters are emitting a very high frequency sound that’s detected by an array of acoustic receivers that we have set up around some of the...