The story of why Navy SEALs exist is, at its core, a reef.
On November 20, 1943, the first wave of Marine landing craft approached the beaches of Betio Island in the Tarawa Atoll. Planners knew the reef was there — it ran parallel to the shore, 500 to 800 yards from the beach. Planners hedged their bet: the first three waves rode amphibious tractors that could crawl over the coral regardless of depth. But the bulk of the assault force would follow in flat-bottomed Higgins boats, and those needed the D-Day tide to lift at least five feet of water over the reef. Major Frank Holland, a New Zealand officer with fifteen years of experience sailing these waters, warned them that November tides here ran unpredictably low. The planners pressed on.
The tide did not cooperate. November 20 fell on a neap tide with the moon at apogee — one of two days a year when the water over that reef barely reached three feet. Landing craft grounded. Ramps dropped in water far too shallow. Marines stepped off into chest-deep water and were cut down by Japanese fire before they could reach the sand. In 76 hours of fighting, more than 1,000 Americans were killed. The casualty rate was unlike anything the Pacific campaign had produced.
The Navy's response was swift and institutional: this could not happen again. The beaches had to be known before the first landing craft left the ships. The obstacles had to be cleared. Men had to swim in ahead of the assault — in darkness, under fire, without support.
Those men would train in San Diego.
Naval Amphibious Base Coronado was formally commissioned in 1944 and quickly became the training ground for the Navy's Underwater Demolition Teams — the men who swam to enemy beaches before dawn, charted obstacles in the surf, and cleared them with demolition charges while defenders shot at them from the shore. They were extraordinary athletes selected, above all else, for their composure under conditions that stripped most people of composure entirely.
The program worked. UDT swimmers preceded nearly every major amphibious landing in the Pacific from 1944 onward. On January 1, 1962, SEAL Team ONE was commissioned here, formally creating the Naval Special Warfare community. The mission broadened — combat diving, direct action, reconnaissance, counterterrorism — but the selection philosophy stayed the same: find out who remains when everything argues for leaving.
Basic Underwater Demolition/SEAL training — BUD/S — runs approximately six months at the Naval Special Warfare Training Center at Coronado. The training has multiple phases: physical conditioning, diving, land warfare. But the moment everyone knows is Hell Week, which falls in the first phase.
Hell Week lasts approximately five and a half days. Candidates run more than 200 miles, often with inflatable boats on their heads. They make repeated passages through Pacific surf that averages around 59 to 60 degrees in winter. They conduct underwater navigation drills while sleep-deprived past the threshold of coherent thought. Instructors manufacture chaos and watch who organizes it. Total sleep over the course of Hell Week: four hours on paper, and far less for most.
In the center of the compound stands a brass ship's bell. It is unremarkable in every physical dimension: cast metal, a clapper, a rope. It is the most important object on the base.
Any candidate can walk to that bell at any time, ring it three times, and the training is over for them. Roughly 70 to 85 percent of BUD/S candidates don't finish — most by walking to that bell and ringing it, some carried off on a stretcher. No one stops them. No one follows. They leave, one way or another.
Those who complete BUD/S go on to serve in SEAL teams that have operated in every combat theater since Vietnam. Their methods, capabilities, and selection standards have shaped special operations forces around the world.
All of it traces back to the beach at Coronado. To the cold Pacific water. To the reef at Tarawa that stopped the landing craft and killed a thousand people because the tide did not rise when the planners needed it to.
The Naval Amphibious Base is visible from the southern bay — low-profile buildings against the Coronado shoreline, the Silver Strand extending south toward Imperial Beach. On some mornings, at certain hours, small groups move on the beach or in the water. They have been doing some version of exactly this for more than eighty years.
That bell is still there. It has been rung thousands of times. Each ring is a choice freely made.
Come see the base that made them, from the deck of JADA, where the Coronado shoreline tells its own quiet story just off the bow.
Hear this story where it happened. JADA sails past this very spot. Join the San Diego Bay History Sail →
Wear the story. Most ring it. A few are carried out. The ones left standing become SEALs. Coronado, California. The Ring It Three Times shirt →