Ruthie Browning dove into the calm, blue water off Key West , Florida, expecting to see “a big, old rock with stuff growing all over it.” She was on a pilgrimage with other Black divers and community members, visiting sacred sites including one where a British slave ship — the Henrietta Marie — sank 326 years ago. The vessel had delivered 200 enslaved people from West Africa to Jamaica and was heading back to Britain in 1700 — near the peak of the trans- Atlantic slave trade — when it was swallowed up in the churning waters of New Ground Reef where the Atlantic Ocean meets the Gulf of Mexico. A concrete marker at the site memorializes the people on that ship. As Browning and her group prepared to dive in early May, the water was calm. The marker, 20 feet (6 meters) below, was visible from the glassy surface. “I thought I’d look at it, pay my respects and that’ll be that,” she said. But something unexpected happened. Tears filled her eyes. She gently told herself: If you can be quiet, maybe they will speak.…