The protected waters of Connecticut and Rhode Island were the site of much of the US Navy's early submarine development efforts, and continue to be even to this day. Many of the Navy's early submarine designs were less than successful, and a number of these boats, some of which were obsolete before they were completed, were used as subjects in weapons tests. If you would like to see a sub closer to home, you may tour the USS Ling in Hackensack.
There are also several German U-boats in the region, most notably the U-853. In the early years of World War II, the u-boats had tremendous success off the East Coast, mainly because practically no effort was made to combat them. These were typically the small Type VIIc and Type IXb submarines, and none of them are sunk off New Jersey or Long Island. The Germans called this 'The Happy Time.'
In the later years, anti-submarine warfare improved tremendously. Although the boats were the larger and more capable Type IXc, they seldom got away without being attacked, and three of them lie in diveable waters, if you call 200-300 feet diveable. And who knows - there may be others.
None of the u-boats that are known to have had action off the New Jersey / New York coastline survived World War II, although the U-123 was raised after the war and put back in service by France. The U-151 of World War I did survive that war, and was sunk as a target in 1921. Also in WWI, the U-156 is assumed to have laid the mine that sank the USS San Diego, and was lost shortly after.
shipwreck, Type IXc/40 U-boat, Kriegsmarine, Germany
Built:
1942, Germany
Specs:
( 252 x 22 ft ) 1051 displacement tons, 48-56 crew
Sunk:
Saturday April 16, 1944
by depth charges and gunfire from destroyer escorts USS Gandy, USS Joyce and USS Peterson after torpedoing tanker Pan Pennsylvania - 44 casualties.
The U-151 was the first German U-boat to operate in U.S. territory in World War I. The U-151 is not actually sunk in these waters ( it was sunk deep off Virginia after the war, ) but it did "contribute" the following six shipwrecks, all on the same day, Sunday, June 2, 1918:
Submarine Defender as rebuilt with sharply raked bow, and her topsides changed, ready for launch at Lake's Bridgeport base. Above her twin propellers is the shutter of a stern torpedo tube. Lake's characteristic pair of amidships planes have been folded up (they are forward and abaft the big conning tower).
A Jon line is a cord used to secure yourself to the anchor line during your safety or decompression stops. This relieves you of having to hold on by hand, which can get tiring for long hangs in a strong current. You can also use a Jon line to get away from the crowd at 15 ft, while still being securely tethered to the boat.
There are a number of prefabricated Jon lines on the market that you can buy, along with several different gadgets to attach it to the anchor line, most of which are clever but not particularly reliable. For a few dollars, you can build a much better Jon line with parts from the hardware store. What you will need is:
6 ft of bungee cord - the kind with a fabric casing