Julian Tusk, “Tusker” to his friends, couldn’t decide which was worse: the acrid stench of the harbor or the detritus-strewn muddy sea floor below it. At least it was cooler underwater. Slightly. He still wore a full-length two-millimeter wetsuit as some protection from whatever permeated this rainbow-sheened soup polluted with diesel, garbage, and a city’s effluence.

There were few fish—living ones, at least. The silty sea bed was littered with the bones of discarded bycatch and cleaned carcasses from the fishermen above, who tossed what wasn’t wanted over the side after their night of hauling in nets offshore. Various invertebrates occasionally scuttled across his limited field of view. He couldn’t name them. Tusker was an archaeologist, not a biologist, and he was braving this toxic morass not for the wildlife but rather to identify a nameless pile of lumber unearthed in yet another of the government’s dredging projects.

The city of Galle lies on the strategic southwestern tip of Sri Lanka. This location made it prized by the country’s European occupiers. First the Portuguese came, building a fort on a cliff high above the sea, with sweeping views from its ramparts across the Indian Ocean. Then the Dutch swept in and ruled for over a century. Finally the British added what was then called Ceylon as a coda to their East India empire. They all made use of the fort and today within its walls is a bustling town bearing the remnants of all three of its former occupiers, in varying states of charming decay: buildings with Mediterranean tiled roofs line dusty streets with Dutch names and distinctly English hotels. Galle Fort is peopled with descendants of all three occupiers, living side by side with local Sinhalese fishermen and Muslim shop owners.

Over its long history, Galle Harbor would have seen any number of its former occupiers’ ships that called on the nearby fort. As he peered through the swirling cloud of silt, Tusker wondered, was this half-buried wooden spine a Portuguese barquentine? A Dutch frigate perhaps? Or just a lowly fishing boat?

Tusker’s six-month stint in Sri Lanka as a visiting professor of marine archaeology meant investigating the glamorous as well as the decidedly less so. A sample of the wood poking up through the thick clay sea bed from this nameless vessel, sent to the lab in Colombo, could help pin down its age and possibly its origin. But something more substantial—a piece of china, a windlass, an anchor—would be more conclusive.

Tusker looked up from his tedious excavating. Through the haze he made out the silhouette of Upali, swimming just above the sea floor ten yards away, jabbing the sand with a long rod. Tusker nodded to him and Upali returned the gesture with a pinkie and thumb “shaka” hand signal. It was typically upbeat for Upali, who made even the most mundane work seem fun.