Poole Harbour

Poole Harbour is a large natural harbour in Dorset, southern England, with the town of Poole on its shores. The harbour is a drowned valley (ria) formed at the end of the last ice age and is the estuary of several rivers, the largest being the Frome. The harbour has a long history of human settlement stretching to pre-Roman times. The harbour is extremely shallow (average depth: 48 cm), with one main dredged channel through the harbour, from the mouth to Holes Bay.

Poole Harbour has an area of approximately 36 square kilometres (14 sq mi) and is one of several which lay claim to the title of the world's largest or second largest natural harbour (including Cork Harbour in Ireland and Halifax Harbour in Canada). There are many significantly larger natural harbours, however, such as New Zealand's 947 km2 (366 sq mi) Kaipara Harbour or San Francisco Bay in California with a conservative estimate of 1,040 km2 (400 sq mi) covered.