The signs were ominous as the Nautilus (SSN-571) edged north in search of a route into the Arctic Ocean from the Pacific. The nuclear-powered submarine's upwardly scanning fathometer detected ice stabbing 30 feet into the depths of the shallow Chukchi Sea between Alaska and Siberia. Through the periscope, Navy Commander William R. Anderson could make out an undulating roof of solid ice, cloudlike and menacing, as the Nautilus slid by in the gray current. The skipper ordered the boat down to 140 feet to avoid collision.
The sub continued bearing north into the unknown, skimming just 20 feet off the smooth sea bottom. Ahead, conditions worsened. Sonar reported a mile-wide block of ice descending to a depth of 63 feet—deep enough to threaten the sub's sail. "I stared in disbelief at its picture on sonar. The books said this couldn't happen!" noted the 37-year-old skipper. The consequences of his 4,000-ton sub smashing into the obstruction and causing severe damage crossed his mind—"slow death for those on board," he mused. In fact, that was in the realm of possibility for the 15 officers, 103 enlisted men, and four civilians on board.