Railroad Bridge between Tottenville and Perth Amboy

>>>There is an old US Navy Hydrographic Office map from the WWI era that shows a floating submarine barrier or net placed at about that location (don't know that it was ever placed there but I suspect not). <<<

There was such a net during the Second World War in the Narrows between Brooklyn and Staten Island. The concrete anchors were and still may be piled in Bayonne south of the ex-Navy Base.

You would have had to have been one gutsy sub skipper to come into NY Harbor. You couldn't submerge enough not to be seen, given how shallow most of it is.

Gutsy they were. During WWI a German submarine made its way into Boston Harbor and actually collided with an electically fired mine. The watch standers heard the sub on their hydrophones, but couldn't find anyone that was authorized to let them detonate the mine. The mine was recovered with gouges from the sub's screw as it passed. I wouldn't be surprised if they invaded or at least tried to invade these waters as well.

Many coastal steamers were sunk off the NJ coast during WWII.

The sinking of so many oil barges led to the construction of the "big inch" pipeline from Texas to NJ. Oil barges burned for hours when they were hit by the Germans. In a few cases, the U-boats shelled them with their deck guns to save torpedos.

Many coastal steamers were sunk off the NJ coast during WWII.

True, but the Nazis were not stupid. A sub might have snuck into NY Harbor but why bother? They could just sit outside and pick off ships at will. The East Coast was an easy target because Americans did such a poor job of blacking out. Sub skippers had an easy time silhouetting ships against the glow.

According to Samuel Eliot Morison's book "The Battle of the Atlantic", The German submarine U-608 laid 10 mines in the NY Harbor on November 10, 1942. The first mine was discovered by a sweeper and the NY Harbor was closed for a period of two days, the only time the harbor was ever closed during the entire war. This corresponds to data from the War Diary of the Eastern Sea Frontier dated November 13, 1942.

"At 1117 Hours, Minesweeper YMS-20 witnessed an under water explosion two miles from Ambrose in 40-25-42N; 73-44-00W, bearing 170 degrees True from minesweeper, range 300 yards. YNS-20 considers explosion actuated by reverse pulse. Column of water 200 feet high was seen. EDC reports all Army mines have been accounted for. Explosion evaluated as magnetic mine or old depth charge. Port entrance closed until 1800/14 while twelve minesweepers operate in area".

If it was only 2 miles from Ambrose, it wasn't in NY Harbor. Ambrose Lights sits miles east of Sandy Hook and Ambrose Channel buoy is also several miles out. I suspect that the sub seeded the channel entrance to the harbor, rather than the harbor itself.

Off topic a bit, but I suspect the definition of "NY Harbor" in wartime probably covered much more than the seascape north of the gap between Fort Hamilton and Fort Wadsworth.

And, into the early and mid-50s there was oil residue now and then coming up onto the North Jersey Coast beaches. On days when this happened around Asbury Park, I'd walk over and watch the Pennsy steams coming through town.