17 eastern and southern boundaries are defined by the estuaries called the New Merwede, the Hollandsch Diep, the Volkerak, the Krammer, and Grevelingen, and the province includes the delta islands of Goeree (Goedereede) and Overflakkee, Voorne and Putten, Rozenburg, Yselmonde, Hoeksche Waard, and Dordrecht.
BRIELLE (Briel or Bril), a seaport in the province of South Holland, Holland, on the north side of the island of Voorne, at the mouth of the New Maas, 51 m.
HELLEVOETSLUIS, OT - HELVOETSLUIS, a fortified seaport in the province of South Holland, the kingdom of Holland, on the south side of the island of Voorne-and-Putten, on the sea-arm known as the Haringvliet, 52 m.
Similar constructions are to be found on the seaward side of the islands of Walcheren, Schouwen and Voorne, and between 's Gravenzande and Scheveningen, and Katwijk and Noordwijk.
The South Beveland (1862-1866) canal connects the East and West Scheldt; similarly in South Holland the Voorne canal unites the Haringvliet with the New Maas, which does not allow the passage of large vessels above Brielle; whilst owing to the banks and shallows in front of Hellevoetsluis the New Waterway was cut to Rotterdam.