Answer
The Central Coast Mariners, an Australian professional soccer club based in Gosford, New South Wales, holds the distinction of being the first A-League club managed by Graham Arnold. His tenure as the Mariners' inaugural coach spanned from the club's inception in 2005 until 2007. Under Arnold's guidance, the Mariners made significant strides, capturing the Premiers' Plate in their debut season and establishing themselves as a formidable force in the A-League.