For 80 years, the wreck of the Vorpostenboot V-1302 John Mahn, a fishing vessel turned German naval patrol boat that sank in 1942, has rested on the floor of the North Sea, a silent feature of the underwater landscape. But the World War II wreck's placid appearance was deceiving. When a team of Belgian researchers studied the sediment surrounding the John Mahn and the microbes that have made the wreckage their home, they found modern-day hazards - hazards that may also be present in other such wrecks. Today, the John Mahn is leaching toxic chemicals, including heavy metals, arsenic and TNT, into the seafloor, according to an analysis published in Frontiers in Marine Science. The steam trawler, which sank after a strike by British Royal Air Force bombers, went down with its weapons and coal reserves.