On January 30, 1925, while working to enlarge the small passage in Sand Cave, Collins became trapped in a narrow crawlway 55 feet (17 m) below ground.

The rescue operation to save him became a national media sensation and one of the first major news stories to be reported using the new technology of broadcast radio.

Although Collins was unknown publicly for most of his lifetime, the fame he gained from the rescue efforts and his death resulted in him being memorialized on his tombstone as the "Greatest Cave Explorer Ever Known".

[6] In September 1917, while climbing up a bluff on the Collins farm, Floyd noticed cool air coming from a hole in the ground.

[7] In December 1917, after further excavation of the breakdown, Floyd discovered the sinkhole entrance to what he would later name "Great Crystal Cave.

If he found a cave, they would form a business partnership and share in the responsibilities of operating the ensuing tourist attraction.

Working alone, Collins explored and expanded a hole within three weeks that would later be called "Sand Cave" by the news media.

Collins managed to squeeze through several narrow passageways, one of which was reported as being no larger than 9" tall, and claimed he had discovered a large grotto chamber, though its existence was never verified.

He worked on creating a more practical entrance to the grotto for several hours a day and weeks on end in order to make it more accessible to tourists.

Collins accidentally knocked over his lamp, putting out the light, leading to misplacement of his foot on what seemed to be a stable wall of the cave.

His younger brother Homer was soon phoned to the scene, and was the only person able to make it through the small passages to get to Floyd before reporter Skeets Miller, Lieutenant Robert Burdon of the Louisville Fire Department, and family friend Johnnie Gerald crossed the boundary in the coming days.

On February 2, 1925, a plan was devised to hoist Collins from the cave using a harness, rope, and the strength of multiple men.

Attempts were made to dig the passages that led to Floyd back out, but rescue leaders, led by Henry St. George Tucker Carmichael, determined the cave impassable and too dangerous, which brought the decision to dig a shaft straight down to reach the chamber behind Collins.

A series of pulley systems were used to remove rocks from the hole, but the pace of work slowed as they dug nearer to Collins.

The 55-foot (17 m) shaft and subsequent lateral tunnel intersected the cave just above Collins, but when he was finally reached on Monday, February 16, by miner Ed Brenner, he was "cold and apparently dead.

Shortly after the media arrived, the publicity drew crowds of tourists to the site, at one point numbering in the tens of thousands.

(The biggest media events of that time both involved Charles Lindbergh—the trans-Atlantic flight and his son's kidnapping—and Lindbergh actually had a minor role in the Sand Cave rescue, too, having been hired to fly photographic negatives from the scene for a newspaper.

Homer Collins was not pleased with Sand Cave as his brother's grave, and two months later, he and some friends reopened the shaft.

They dug a new tunnel to the opposite side of the cave passage and recovered Floyd Collins' remains on April 23, 1925.