A water taxi capsized and killed five people in Baltimore Harbor in 2004 because excessive passenger weight made the boat too unstable to withstand a sudden gust of wind, the government said Tuesday.
The National Transportation Safety Board said the Coast Guard underestimated the "tippiness" of the 36-foot Lady D pontoon boat because it had conducted the wrong stability test on the wrong vessel.
The Coast Guard also assumed the average weight per passenger was 140 pounds, a standard that hasn't changed since 1942, the safety board said.
"It's the issue of what this thing can carry," said NTSB Chairman Mark Rosenker.
The average weight among the Lady D's 25 passengers when the accident happened was 168 pounds, making it 700 pounds overweight, investigators said.
The Coast Guard has implemented a more detailed stability test for pontoon boats like the Lady D as a result of the accident.
In October, the Coast Guard contracted for a one-year study to assess what would happen if the assumptions about people's average weight were changed.
The NTSB said it was concerned the Coast Guard wasn't moving fast enough.