The Exe Estuary extends for some 12 kilometres from the harbour entrance (Pole Sands) to Countess Wear and a further 3 kilometres to Town Quay, Exeter. The Estuary is protected from the open sea by Dawlish Warren, a natural sand spit, and by Pole Sands which forms a natural breakwater between the approach navigation channel and the open water.
At low tide two third of its water area dries out, revealing sandbanks, mudflats and eelgrass beds which provide important habitats for marine life and feeding birds. The limited extend of water restricts navigation and also the areas that can be used for deep water moorings.