<Dd> On the west . A line joining Isle Vierge (48 ° 38 ′ 23" N 4 ° 34 ′ 13" W ﻿ / ﻿ 48.63972 ° N 4.57028 ° W ﻿ / 48.63972; - 4.57028) to Lands End (50 ° 04 ′ N 5 ° 43 ′ W ﻿ / ﻿ 50.067 ° N 5.717 ° W ﻿ / 50.067; - 5.717). </Dd> <Dd> On the east . The southwestern limit of the North Sea . </Dd> <P> The IHO defines the southwestern limit of the North Sea as "a line joining the Walde Lighthouse (France, 1 ° 55'E) and Leathercoat Point (England, 51 ° 10'N)". The Walde Lighthouse is 6 km east of Calais (50 ° 59 ′ 06" N 1 ° 55 ′ 00" E ﻿ / ﻿ 50.98500 ° N 1.91667 ° E ﻿ / 50.98500; 1.91667), and Leathercoat Point is at the north end of St Margaret's Bay, Kent (51 ° 10 ′ 00" N 1 ° 24 ′ 00" E ﻿ / ﻿ 51.16667 ° N 1.40000 ° E ﻿ / 51.16667; 1.40000). </P> <P> The Strait of Dover (French: Pas de Calais), at the Channel's eastern end, is its narrowest point, while its widest point lies between Lyme Bay and the Gulf of Saint Malo near its midpoint . It is relatively shallow, with an average depth of about 120 m (390 ft) at its widest part, reducing to a depth of about 45 m (148 ft) between Dover and Calais . Eastwards from there the adjoining North Sea reduces to about 26 m (85 ft) in the Broad Fourteens where it lies over the watershed of the former land bridge between East Anglia and the Low Countries . It reaches a maximum depth of 180 m (590 ft) in the submerged valley of Hurd's Deep, 48 km (30 mi) west - northwest of Guernsey . The eastern region along the French coast between Cherbourg and the mouth of the Seine river at Le Havre is frequently referred to as the Bay of the Seine (French: Baie de Seine). </P>

Where does the english channel end and the north sea begin