Question: What city situated at the northern extremity of Brisbane Water, is also where the Central Coast Mariners FC is based?
Context: Central Coast FC, formerly known as "Central Coast Lightning" is a semi-professional soccer club, based and located on the Central Coast of New South Wales.  They are the main "feeder" club for the professional A-League club, the Central Coast Mariners ! Central Coast Mariners .  As well as fielding a team in the NSW National Premier Leagues Division 2, they also have junior clubs that have teams as young as Under 8, which play in the various club competitions along the Central Coast. Gosford is a suburb located on the Central Coast of New South Wales, Australia, about 76 km north of the Sydney central business district.  The city is situated at the northern extremity of Brisbane Water, an extensive northern branch of the Hawkesbury River estuary and Broken Bay. Central Coast Mariners Academy is a semi-professional soccer club based in Gosford , New South Wales, Australia.  It serves as the youth and reserve team for A-League club Central Coast Mariners ! Central Coast Mariners , and participates in men's, women's, and youth competitions in the National Premier Leagues system as well as the National Youth League and Football NSW Skills Acquisition Program. Brisbane Water is a wave-dominated barrier estuary located in the Central Coast region, to the north of Sydney, New South Wales, Australia.  Brisbane Water has its origin at the confluence of the Narara and Coorumbine Creeks, to the south–east of Gosford and travels for approximately 18 km in a southerly direction to its mouth at Broken Bay, about 7 km from the Tasman Sea, at Barrenjoey Head.  A number of towns surround the shores of Brisbane Water, including Booker Bay, Davistown, Ettalong Beach, Gosford, Green Point, Kincumber, Phegans Bay, Saratoga, Wagstaffe, and Woy Woy.  Contained within Brisbane Water is St Huberts Island, Rileys Island, and Pelican Island; and adjoining the estuary is Brisbane Water National Park to the west and Bouddi National Park to the east. The Central Coast Mariners FC, also known as the Central Coast Mariners Women, represented the Central Coast Mariners in the Australian Women's National Football League, the W-League for two seasons between 2008 and 2009.  In July 2010 it was announced the team would not be entered in the 2010 W-League, due to lack of funding.  There is hope that the team may reenter the competition in a later season. The Central Coast Mariners' season 2006-07 was the second competitive season of football (soccer) club Central Coast Mariners FC.  The club hoped to build on their strong performance in 2005-06, which included a Pre-Season Cup title, a finals appearance in the World Club Qualification playoff and their participation in the inaugural A-League grand final. Jake McGing (born 22 May 1994) is a professional Australian footballer who plays as a central defender for Central Coast Mariners FC in the A-League.  On 11 August 2015, he made his professional senior debut for Central Coast Mariners FC in the 2015 FFA Cup against Wellington Phoenix FC. The 2012–13 Central Coast Mariners season was the Central Coast Mariners ! Central Coast Mariners 's eighth A-League season.  It included the 2012–13 A-League season (and the competition's subsequent finals) as well as the 2013 AFC Champions League. Patrick Zwaanswijk (born 17 January 1975) is a semi-professional Dutch footballer who currently plays for and captains Southern & Ettalong United in Australia's Central Coast Premier League.  A product of the Ajax Youth Academy, Zwaanswijk retired from professional football in 2013 following stints with FC Utrecht, Oita Trinita, NAC Breda and Central Coast Mariners FC.  He has played predominantly as a central defender throughout his career. Central Coast Mariners Football Club is an Australian professional soccer club based in Gosford, on the Central Coast of New South Wales.  It competes in the A-League, under licence from Football Federation Australia (FFA).  The Mariners was founded in 2004 as one of the eight original A-League teams.  It was the first professional sports club from the Gosford region to compete in a national competition.  Despite being considered one of the smallest-market clubs in the league, Central Coast Mariners has claimed one A-League Championship from four Grand Final appearances and topped the table to win the A-League Premiership twice.  The club has also appeared in the AFC Champions League four times.
Answer: Gosford