Ron Masters, the department commissioner, said that boaters must proceed with extreme caution through the South Shore’s marshes and bays for months to come. Undiscovered debris could be hidden just under the water’s surface, and speeding through channels that were once easily navigable could lead to disaster. “It’s a catastrophe if they hit something hard,” he said.

Town officials and university researchers have been methodically mapping the wetlands anew to check for changes in water depth, but it will be some time before they complete reconfigured maps.

Watch for the sheen on the water

One of the town’s toughest challenges has been cleaning up gasoline and oil tanks that were strewn across the wetlands by the storm. In the days after Sandy hit, town and federal Environmental Protection Agency officials surveyed the South Shore by helicopter, looking for the telltale multicolored sheen that indicates a fuel spill in the water. The town removed numerous tanks in its barges, but there are still some out there.

“We had one the other day,” Masters said. “You can see the sheen right away.”

Leaking oil tanks are particularly worrisome for Don Harris, SPLASH’s educational director and one of the organization’s founders. “Don’t swim in the water until it’s tested and deemed safe,” Harris said. “Boats [and cars] were destroyed. Gasoline and transmission fuel leaked. There was asbestos contamination from insulation. It’s frightening.

“The animals,” he noted, “are in a much more polluted environment.”

Maritime history lost?

Harris added that many, if not most, of the tiny bay houses that dotted the wetlands were damaged or destroyed in the storm. Bay houses, the first of which were built on the South Shore 300 years ago, reached their height of popularity after World War II. Then, after passage of the Water Quality Act of 1965, the town stopped granting permits for them. Building on the wetlands was seen as an intrusion into the natural world.

Many bay houses were taken down, but three dozen remained, and they have served as havens for local fishermen through the decades, passed down within families. Now their fate is uncertain.