His companion vessel was sent in pursuit of a corsair, so that the _Philadelphia_ was left alone to perform blockade duty.

On the last day of October, 1803, Captain Bainbridge observed a Tripolitan vessel trying to make port.

He gave chase, but the coast was dangerous, abounding with shoals and reefs, with which the fugitive vessel was familiar, while Captain Bainbridge had to keep sounding and regulating his speed in accordance with the degree of danger.
In the midst of the pursuit, and while every precaution was taken, the crew, to their dismay, heard a dull, grating sound, whose meaning they well knew; the bow of the frigate rose six feet out of the water, and the stoppage was so sudden that nearly every one was thrown off his feet.
A hurried examination showed that the _Philadelphia_ was inextricably fast, and could not be freed until the tide rose.

Meanwhile the corsairs would issue from the harbor near at hand, and, choosing their own position, batter the frigate to pieces and kill or make prisoners of the crew.
Every possible effort was made to release the ship, but she was too firmly spiked on the jagged reef to be budged, and the dreaded peril speedily appeared.

The Tripolitans soon discovered the plight of the American, and nine gunboats hurried out from the harbor.