A third-rate, two-decker, 74-gun warship is shown flying the red ensign and private pennant on the left of the picture, in the entrance to Port Mahon harbour. A ship of this size could have been used for lying in line of battle, as an independent cruiser or the flagship of a small squadron. This one is in fact hove-to and making little way, to drop a boat which is conveying two naval officers to the quayside on the right. The boat, also flying the red ensign, has a smartly uniformed crew which suggests it is taking the captain ashore. Other ships lie behind off the harbour entrance. In the foreground is a variety of small craft including a rowing boat on the left, with a man holding a net spread over the water. In the central foreground a felucca, a type of narrow, swift, lateen-rigged sailing vessel used in the Mediterranean, moves towards a small landing stage. The buildings of the port are visible on the right and the 18th-century lazaretto or hospital to the left. The artist has incorporated detailed elements of everyday life, such as washing hanging on a line, a woman carrying a basket on her head, a man with his fishing rod and inhabitants wearing their traditional dress. This is an unusual, large composition by an artist more widely known for small-scale paintings in the Dutch manner and stylistically it hovers between the 18th and 19th centuries.

Powell came from Chichester and spent some time at sea. This is not one of his exhibited works and was probably therefore a commission, perhaps for the captain of the unidentified vessel shown. It is signed and dated 'C M Powell 1820' in the bottom right-hand corner.