The given coordinates will take you to a plaque commemorating the opening of the park. You will need to collect some numbers and do some maths.
The President of the Board served from ABCD until EFGH
The cache is located at S 32 46.AXH - where X=B-2 and E 151 47.HZH where Z=A+E
Enjoy the view and check out the current water level while you are there. This dam and the adjacent sand beds provide much of Newcastles drinking water.
Caution - the public toilets at the end of the park are very dodgy :-(
The Park is also under the Norther approach to Williamtown airport, so there might be aircraft flying low overhead - including RAAF jets. If they have two tails they are FA/18 Hornets, if they are small with single tail they are Hawk Fighter Trainers. Both of these types will normally be in pairs or multiples of two. Small grey propellor driven aircraft are PC9s - used as a cheaper alternative to train the ground based people who direct air to ground attacks. If it is large (737 size) and grey with a surfboard on the back - it is a Wedgetail Airborne Early Warning and Control aircraft - ie an airborne radar and communications hub.