About the USS New Jersey: she is retired and doing museum duty in Camden, NJ on the Delaware River where she was built, right across the water from Philadelphia. I haven't had a chance to visit yet, but my brother and father have been aboard and were very impressed.
The Jersey is one of 4 Iowa-class battleships built, and all four still exist. Iowa and New Jersey are both floating museums, now, I'm not sure about Missouri and Wisconsin, they may still be on the reserve list, but they are not likely to ever see service again. I have heard that when those ships were used in the 80's and in '91 they were still using the old mechanical analog ballistic computers that are built into them and linked by gears and shafts from the gun turrets to the CIC; I don't know if that's true, but I love old machinery like that. Can't wait to get a look for myself.
As for U-boats, there is a sunken U-boat off the coast of North Carolina, U-352, I think it is, and it's a very popular SCUBA dive site. I've dived on it at least 3 or 4 times. It was found by a local dive shop back in the 70s, and the U.S. Navy quarantined it for a while, until they could remove all the remains of German sailors to send them back to Germany, and also to remove or disarm all the live ordnance they could reach. There are still live torpedos aboard, but they are inaccessible without ripping the ship open. The boat is basically intact, laying over on about a 45 deg angle, in 110' of water. The top of the conning tower is about 80' or 85', the hatches have been removed, as have the screws and the AAA gun, which currently sits on the dock at the dive shop in Atlantic Beach. No one has ever reported finding the deck gun.
The rudders are still there, and parts of the outer hull have eroded away (or were blasted away by the Coast Guard cutter that sank her), so you can see some of the machinery on the shafts, perhaps the stuffing box or electric motors. The bow is almost broken off and bent to one side, she may have landed nose-first in the sand. The hatchways are small in diameter and it's pitch dark inside, but if you stick a flashlight in you can see some hardware. You don't dare go into that tight space with SCUBA gear if you know what's good for you.
About half her crew survived the action, and some of them returned to the site for a ceremony back in the 80's or 70's.