What matters more in history, the great events that happened, or the crucial things that never occurred? “D-Day Beneath the Waves” (8 p.m., Discovery) examines a secret weapon that did not work as planned, and a momentary fiasco that may have cost thousands of lives.

As viewers of the D-Day drama “Saving Private Ryan” must remember, American infantry were ripped by German machine gunfire as they waded ashore on Omaha Beach. That wasn’t supposed to happen. The army had developed a special floating tank, known as the Sherman DD, designed to arrive before the infantry hit the beach. The Sherman DDs successfully embarked upon the Utah and Sword beachheads and provided cover for the infantry. But the tanks floundered and sank off the shores of Omaha beach, exposing the Americans to deadly fire.

“Beneath the Waves” combines historical footage, dramatic reenactments and interviews with American and German veterans to paint a vivid portrait of June 4, 1944. Nearly 60 years later, veterans still appear awed by the size of the Allied invasion armada. As one German veteran recalls, “there seemed to be more ships than there were German soldiers.”

Underwater archaeologist Brett Phaneuf led a diving team that discovered the barnacle-covered remains of 13 sunken DD Sherman tanks. Nothing quite conveys the humbling passage of time as the sight of a crab scuttling across a once mighty war machine. Phaneuf also studied tidal charts and beach currents to determine the unique conditions that doomed the Omaha-bound tanks. Well worth watching, “Beneath the Waves” combines solid history and intriguing detective work.

A&E presents new episodes of “Minute By Minute” (9 p.m.) the documentary series that chronologically reconstructs historical events from the perspective of participants and eyewitnesses. In the coming weeks, “Minute by Minute” will look at the 1981 attempt on President Ronald Reagan’s life, the 1989 San Francisco earthquake and the infamous 1994 O.J. White Bronco chase.

Tonight’s “Minute by Minute” recalls the story of Dr. Jerri Nielsen, the South Pole based doctor who diagnosed her own breast cancer, and who, with the help of her fellow scientists, performed a biopsy on herself. Nielsen, her family members and fellow “Polies” recall her race against time as well as the brave efforts of flight crews who defied minus 70 degree conditions to air-drop medical supplies and later extract Nielsen from the bottom of the world. This is an inspiring tale of courage and camaraderie under harrowing conditions.

Tonight’s other highlights

Two teams compete to build a powerful drill on “Junkyard Wars” (5 p.m., TLC). The series will broadcast two new episodes at 5 p.m. and 6 p.m., every Wednesday through June 26.

Scheduled on “60 Minutes II” (7 p.m., CBS): Stem cells contribute to one boy’s startling recovery.

While preparing to testify about Bartlet’s medical cover-up, Leo flashes back to a difficult moment on “The West Wing” (7 p.m., NBC). Caution: this episode contains a rather peculiar product placement for an expensive brand of scotch whiskey.

Mary Louise Parker, Peter Gallagher and Bebe Neuwirth star in the 2000 made-for-TV romance “Cupid & Cate” (8 p.m., CBS).

NBA playoff action (8 p.m.).

“Boston 24/7” (9 p.m., ABC, part 2 of 6) examines an embattled high school principal and a prosecutor preparing his case against a rapist.

Cult choice

Starring Robert De Niro, James Woods and Elizabeth McGovern, director Sergio Leone’s 1984 epic “Once Upon a Time in America” (7 p.m., AMC) spans 50 years in the lives of Brooklyn gangsters. Edited for television.