On March 6, 2004, the small passenger vessel Lady D, a pontoon water taxi with 2 crewmembers and 23 passengers on board, was en route from Fort McHenry to Fells Point, Maryland, when it encountered a rapidly developing storm with high winds. The pontoon vessel began to roll in the waves and eventually continued over onto its starboard side and capsized. Major safety issues discussed in this report include passenger weight criteria for stability assessment; pontoon vessel stability standards; and policies and procedures pertaining to weather operations. As a result of its investigation of this accident, the Safety Board made safety recommendations to the U. S. Coast Guard.