While the battle raged at Fort Mercer, American and British naval forces exchanged intense fire on the Delaware River. Earlier in the fall of 1777, American forces had sunk chevaux de frise, racks of wooden, spiked spears, in the river, which proved difficult for British ships to navigate. During the conflict, two British ships, the Augusta and the Merlin, caught fire after running aground. The Augusta exploded the next day in a blast so loud it was heard as far north as Germantown in Philadelphia.
