The Fleet lagoon was originally created when Chesil Beach seperated from the shoreline, the fleet measures approximately 8.2 miles in length and covers an area of around 480 hectares, the width of the lagoon various dramtically from around 900 meters at Littlesea to as little as 65 meters at The Narrows. The depth of the lagoon various too, at its deepest it measures around 4.5 meters, although most of the fleet is around 2 meters deep.
The Fleet is connected to the sea via a narrow channel positioned at Ferrybridge providing access to Portland Harbour, seawater can also enter the lagoon through Chesil Beachs stony embankments with the correct tidal conditions. Fresh water also enters the lagoon from a variety of small streams from the surrounding countryside.
The fleet offers a natural habitat to a wide variety of sea and bird life and forms part of the Fleet Nature Reserve.