About a mile long, in the Assunpink WMA. To the east you can find two other small lakes in the same watershed: Stone Tavern Lake, and Rising Sun Lake. Assunpink Creek drains into Lake Mercer, which is much larger than any of these.
More: Assunpink Lake (Upper Freehold) ...
The marker in the lower-center of the map is a super-easy put-in on Whale Creek. The other markers are a longer slog over the beach. All have convenient free parking (don't leave your vehicle in the launching area, that's a dick move!)
More: Cliffwood Beach (Aberdeen) ...
This lake has a lot of different branches to explore, and you can actually go quite a long way. The two marked sites are the best accesses for the northern and southern branches of the lake. Unfortunately, located in the middle of Asbury Park, the water is not the cleanest, especially near the railroad and toward the drain at the beach. The 'headwaters' are better.
More: Deal Lake (Asbury Park) ...
Lake Lefferts is a man-made lake, the result of the construction in 1928 of Lake Lefferts Dam, which captures and stores the flow of Matawan Creek. This is the nicest spot in northern Monmouth County. The lake is in three parts:
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More of a pond than a lake, only about half a mile long, but accessible in Thompson Park. Never actually been there. Nearby Swimming River Reservoir is completely off-limits, even to the people that live on it!
More: Marlu Lake (Tinton Falls) ...
Prospertown Lake is not a park, it is a "Wildlife Management Area", and falls under a completely different set of regulations, which you can find here:
From the state website:
Any vehicle used to transport or launch a vessel or water conveyance on the following WMAs must have affixed to the lower corner of the driver’s side rear window a Boat Ramp Maintenance Permit or a photocopy of a current hunting, fishing or trapping license showing the Conservation ID Number (CID#). Identifying information other than the CID# may be blacked out to protect your identity. Boat Ramp Maintenance Permits may be purchased for a fee of $15.00 from any license agent or Fish and Wildlife’s license Web site (under “Wildlife Management Area Use Permits” after logging in and selecting to make a purchase).
This is a nice clean lake that straddles the border between Monmouth and Ocean Counties. The neat thing about it is, if you scroll the map to the upper-right corner, that is not some industrial park, that is Great Adventure! This is the lake that is at the back of the park. At the east end of the lake, you are looking up at all the rides, while to the south is the Safari Park. You can see more water from there, but I wouldn't jump any of the dykes, as that would put you on Great Adventure's property, or maybe in the lion pen. It's not a big lake, but there is plenty of shoreline to inspect. There is a small dam at the western end. No real facilities, just parking.
More: Prospertown Lake (Jackson) ...
I have marked Lot C on the bay side, which is the best combination of parking and access to the water. This spot is very popular with windsurfers. You could also use Spermacetti Cove to the north. On a very fine day, you could even try the ocean side.
More: Sandy Hook ...