If you're heading to the Shore for the 4th (or are already there), water temperatures are going to be a bit of a shock to the system from time to time. While warm water lurks out in the Atlantic offshore a ways, upwelling has taken hold along portions of the immediate coast, leading to rather chilled pockets of water that have held consistently in some places.
Upwelling is when cooler water is pulled towards the surface while warmer water pushes offshore. This can happen with a surface air current of south-southwest or southwesterly, warmer water is pushed along the coast towards the northeast, with cooler water pulled up at the immediate shoreline.
Water temperatures vary along the Jersey Shore from the upper 50's to around 70, depending on location. Barnegat, for instance, had a 15 degree swing in temperatures along the coastline during the morning hours, followed by a 14 degree drop a few hours later despite a consistent wind from the south-southwest through the day. The temperature variance at Barnegat coincided with tides...low tides producing lower temperatures (lower water levels near the coast providing more of an opportunity for the colder water to slip in), higher tides producing higher temperatures.
It's a bit of a different situation at Atlantic City -- water temperatures varied here as well but not to the same extent. They are, on the whole, colder...generally in the 50's and low 60's...but vary less than they did up at the coast at Barnegat Light.
Water temperatures are warmer in Delaware Bay (around 70 degrees), running closer to normal for this time of the year. "Normal" water temperatures along the coast should run in the upper 60's to 70 degrees.
The prevailing wind direction over the coming days is southerly or southwesterly, so upwelling may remain a bit of an issue for the next few days...and the result of it is an ocean that may provide you a bit of a shock to the system as you jump in to get relief from the summertime heat.