By World War II, the history of the Chesapeake Bay and the submarine had become fully intertwined. While no Nazi submarines officially penetrated the Chesapeake, there's an ongoing discussion among old-timers around Willoughby Spit who swear there is the sunken hulk of a submarine there. Some remember playing on her emergent hull as youngsters and say they even went below and looked at the controls.

Joseph Judge, a Norfolk-based historian with the U.S. Navy, is certain that the wreck is the USS Stringham, a torpedo boat struck from the Navy list in 1913. While under tow to the scrap yard in 1923, it broke loose, became grounded and was abandoned, he said.

Most likely, the nearest an enemy German sub came to the Chesapeake was U-701. It torpedoed the 7,000-ton tanker British Freedom near the Chesapeake Lightship. Freedom limped into Norfolk for repairs. Later, while laying mines near the Bay mouth in 1942, the U-boat was sunk off Hatteras.

Many of the ship's dead were brought ashore and interred with full military honors at Hampton Roads. The submarine provides a somewhat difficult recreational dive site today.

The tales are persistent, though, about intrusions elsewhere along the coast. One claims that a sub came up in the Verrazano Narrows, close enough to Manhattan that the crew took pictures, which reportedly still exist, of the New York City skyline at night. There is no doubt that dangerous spying took place along the Atlantic Coast.

The large U.S. Naval Amphibious Training Base near Solomons Island, MD, was placed virtually atop a once-tiny fishing village of 300 people, where nearby sand beaches were available to train for mock invasion landings. The site was believed to be entirely out of sight for prying German U-boats. Heavy steel submarine nets, buoyed along the surface, were stretched in long lines across the James River mouth from Willoughby Spit to Hampton Roads to defend the Naval bases, with a floating gate opened when necessary by tugboat.

The Bay mouth, about 16 miles wide, was impractical to net and was defended by mine fields, surface patrols and observers. The fear was plausible. After all, Deutschland, the pre-WWII German cargo submarine, came right up to Baltimore and was welcomed. So it was hardly impossible for a clever U-boat skipper to work his way up the Chesapeake and raise serious havoc in Maryland's heartland.

Solomons, after the base was decommissioned in August 1945, was never quite the same. When my wife and I moved to Southern Maryland in the early 1970s, the fake hull of a ship, complete with boarding nets, lifeboat davits and a pool of water at the bottom, still stood on the old base site, like an out-of-place movie set. There, troops by the thousands were trained not only for debarking and invasion, but for getting away from a ship if torpedoed. Not far away in the Patuxent River, during and after the war, the Navy was developing underwater mine technology to take out potential enemies.

The S-49 was built in 1922. It was 220 feet long, with beam of almost 22 feet and displacing 990 tons. This class of submarines formed the backbone of the U.S. underwater fleet in the 1920s and 1930s. In 1936, S-49 was sold off to Baltimore for salvage and stripped-demilitarized-to a still-floating hulk.

The sub had an odd life thereafter; it exhibited in various U.S. cities, where it was open to the public. At the Great Lakes Exposition in 1936-37, a big "C" (for civilian) was painted on each side of its bow and the sub was reputedly painted yellow, perhaps making it the original "Yellow Submarine."

Still moveable and structurally intact, the sub was reacquired by the Navy and taken to the Patuxent Naval Mine Warfare Test Station. Fitted to submerge and surface by remote control, it was targeted with various underwater explosives, a testing program that according to the old-timers at the Chesapeake Biological Laboratory, killed countless numbers of migrating and resident fish-all for the war effort, of course.

On Dec. 16, 1942, while under tow in the Patuxent, S-49 foundered and sank in 125 feet of water just north of Point Patience, one of the deepest points in the Chesapeake. (This unusual depth anomaly had been noted by Capt. John Smith during his 1608 exploration of the Bay.)

Thereafter, as late as the 1970s, the sub was used for training Navy hard hat divers, who slowly cut down obstructions on her hull and sealed the openings to the interior. In the early 1990s, S-49 also was a dive site for civilian divers.

This is no wreck for amateurs, though. The Patuxent water column is in profound darkness below about 50 feet, and visibility, even with bright dive lights, is said to be barely 5 feet. The hull and superstructure rises about 11 feet off the bottom amid fierce currents that rage in all but slack tide.

A NOAA employee I met in the 1990s said that when he dove on the S-49, the hull was festooned with tough monofilament fishing line that could trap scuba tanks and snag respirators. He got out of there quickly, but did note that large numbers of oysters had set on the steel hull.

Once submarine warfare became a terror on the seas, a major challenge was how to detect and defend against their attacks before they were within torpedo range. Echolocation, which uses the now-common technology of sonar, was developed about 1906 and remained in its infancy for decades. The principals were developed thanks to the work of Reginald Fessenden, who pioneered "radiotelephony" transmission through the air at Cobb Island in the Maryland Potomac. His ideas morphed in 1915 to an early "fathometer," or depth sounder, a version of sonar that is aboard almost every sizable commercial and recreational boat on the Bay today.

The technology was developed too late to be of significant use locating submarines during World War I, but in anticipation of the "next" war, a workable product was ready for submarine combat in World War II.

Portsmouth Navy Yard, at the mouth of the James River in Virginia constructed L-8, the first submarine to be built in a Navy shipyard. (An earlier submarine, Plunger, was built by the John P. Holland Torpedo Boat Company in Baltimore under a Navy contract, but was not built in a Navy yard. [See "Past is Prologue," May 2010.]) Much later, from 1941-44, activity was frantic as the yard built submarines in as little as 173 days, launching as many as four in a single day and turning them out at a rate topping 30 annually.

The Nazis and Japanese in submarines were desperate to avoid detection by sonar, a discovery that would invariably be followed by depth charges. German engineers fitted about 10 submarines with a complete covering of rubber anechoic tiles designed to absorb, not reflect, sonar sound wave pulses. The unterwasserboot U-1105 was one of these. Launched in 1944, it patrolled Allied convoy routes off Ireland until spring 1945.

It sank one of the convoy vessels, then hid on the bottom, silent and protected from sonar by the absorbent tiles, until the search for it was abandoned. The rubber sub became known as the Black Panther and went undetected in the North Atlantic for the rest of the war. Kriegsmarine Kommandant Adm. Karl Donitz sent the crew of Black Panther its final message, ordering surrender and ending the war with Germany. Only then was it taken by Allied forces.

The U-1105 was later brought to the United States so its anechoic tiles could be studied. After U.S. engineers learned what they could, the sub was towed to Maryland's Patuxent River to be used as a target for anti-submarine measures. During one of these tests off Point Lookout, a peninsula between the Patuxent and Potomac rivers, it sank. The U-1105 was raised from the bottom and in 1949 faced yet another round of explosives. This time the blasts split its hull around from deck to keel, a wound from which it would never rise again. Thus abandoned, it was lost to history.

Chesapeake Bay waters off the Potomac mouth retain good clarity well into June, by which time the water has also warmed enough for recreational diving. On June 29, 1985, Uwe Lovas led a team of sport divers and found U-1105 about a mile west of Piney Point, a discovery that led to the sub's eventual designation as Maryland's first historic shipwreck preserve. The site is buoyed between April and December for recreational divers.

Once, in May 1987, after anchoring out overnight, I headed out of the Patuxent bight on a light spring southwester. To my surprise, out of the predawn haze emerged a Navy submarine. On the light wind, my ketch slowly approached the vessel, which clearly was riding between two anchors, affording me a close approach and look at the sub. On the bow and stern were vertical fins, almost like those on a shark, rising from the deck.

I could find no appendages like these on any World War II era submarine in books, but research later identified this vessel as the USS Blenny, a Balao Class sub of World War II vintage. It was the first of its kind to have a newly strengthened pressure hull made of titanium-manganese alloy steel nearly an inch thick. The steel weighed 35 pounds per square foot and enabled diving to 450 feet. The USS Blenny was an active combat sub in the Pacific. Under Lieutenant Commander W.H. Hazzard, it sunk 80 ships, totaling 43,000 tons, in 10 months. It remained commissioned until 1952. The two "shark fins" were transponders for the sub's passive sonar listening device.

The word in nearby Solomons harbor was that she was there as a target, and might later be turned into a fishing reef or dive site. Advocacy for this latter constructive fate was the work of John Foster, who worked for the Maryland Department of Natural Resources. Then-Sen. Roy Dyson managed to get legislation passed that enabled the sub's acquisition by Maryland as a dedicated artificial reef. It was sunk with explosives, and great clouds of smoke and flame, 12 miles from the Ocean City Inlet, on June 7, 1989. From a nearby observation vessel, Skipper Hazzard and nine men from its original crew witnessed their old ship taking on a new sub-sea life.

When my generation was in its teens, it was pretty hard to get time alone with one's girlfriend. Along the inlet and river where I spent my youth, those with cars would park there in the dark and, as the saying went, "watch the submarine races."

In the last couple of decades, the Chesapeake has had actual submarine races, which generate a lot of interest in the trade magazines of naval architecture and ocean sciences. Dan Dozier, a Navy structural engineer explained that these races involve submarines that are totally person-powered, like the earliest submarines, but with a century-and-a-half of engineering innovation and invention to advance the art. Teams from all over the country compete.

At the competition in 1989, there were 19 entrants and the race started at the Washington Navy Yard, just across from the U.S. Navy Museum. Flooding problems from the Anacostia led to the event's being moved to the Admiral David Taylor testing facilities near the Potomac River at Carderock, MD. The facilities' basins, which are used to test ship models and ocean engineering projects, have 3,200 feet of longitudinal tanks, although the actual straight-line timed speed trials are 100-meter-long courses.

At first, the races took place annually. Now they are scheduled every two years in June; the next is in 2011. The Navy and the Foundation for Underwater Research are the sponsors.

There is a core of constant annual participants with other teams coming and going. In 2007, there were 19 teams and a total of 22 boats, including American, Canadian and Dutch entries. An audience of 450 watched; TV and screen personality Alan Alda covered the event for Scientific American.

Most intriguing to me were entries named Faux Fish and Trigger Fish, which had articulated bodies that undulated like real fish. They were capable of going 1.1 knots underwater and could negotiate an underwater slalom course. One less whimsically powered Canadian sub, OMER, topped 8 knots underwater, which would handily beat most of the Chesapeake's 19th century contenders-at least until the two young, energetic crew got tired.