Fishing is usually pretty good in Mantoloking. I like to fish in Normandy/Normandy Shores and Brick Beach which is not far. I think it is probably less fished there by beach because of parking difficulties, which you will be able to avoid.
From my limited trips out, there seems to be a few good troughs running just a few feet paralel to the beach. These troughs seem to run for a couple of miles. On the other side of the trough is a 6-10 foot wide sandbar followed by a sharp drop off. The troughs seem to be about 4-5 feet deep at high tide and on the other side of the sandbar the water is much deeper. The troughs will hold fish, especially in any rips through them or any areas leading back out into the deeper water.
Of course, this could change, almost daily! Especially with the weather that has been through the area recently. Your best bet is to read the sand and water when you get out there or look for the bait and birds. If you are going to bait fish or dead stick it, pick a good area and give it a shot. If you are lure fishing, you can move around and hit multiple spots much quicker. Fish wise, you will probably find blues and bass...maybe some fluke, but a little early for them.
Besides that, just be careful. That water is still cold...too cold to wade out without waders so.
Good luck and catch 'em up!