One mystery was solved when he got his first look at the side of the giant float. The top layer was just a thin veneer of slate while the rest of it was metal. When he tapped it, it rang hollow. The metal had withstood centuries of immersion in salt water because the designer had covered it in a layer of fine gold flake. Gold never corrodes, and could protect the metal float for centuries.

There were marks in the gold, thin lines cut through it as if someone had scraped some away with a knife. He imagined it had been one of the Ronish boys thinking the whole drum was made of gold only to see it was just a patina not even a millimeter thick. Where the knife had left scars, Juan could see that the float was made of bronze. While this metal resisted corrosion better than steel, he figured in another couple of decades the sea would find a way to eat through the scar. The hollow float would fill with water, and the trap would never work again.

Cabrillo estimated the drum was ten feet tall, and when the bottom of it finally passed over his head it stopped in line with the top of the niche. It had to have hit another small projection from the shaft wall that he had overlooked on his way down. He marveled at the engineering it took to make this work.

He swam out of the niche and looked up. There was a handle on the underside of the float. He grabbed it and tugged. The buoyancy had been so perfectly calculated that he was able to pull the enormous contraption downward a bit. He knew he could get out by tying his lead weight belt to the handle and letting the float settle back to the bottom while he waited in the niche. He assumed that’s what the Ronishes had done, only their weight had dropped away. He descended past where the bottom of the shaft had been and sank lower still.

In the exact center of the real floor of the Treasure Pit he found a pile of rocks from the beach. The Ronish brothers’ counterweight. The bag that had once held them had long since been dissolved by the Pacific’s salt water. The other discovery Juan made was far more intriguing. There was a low tunnel off the main vertical shaft.

Cabrillo entered it, his tanks tapping on the ceiling because the fit was so tight. The tunnel angled up sharply, forcing him to pause several times in order to let the excess nitrogen dissolve out of his system. He checked his air supply. If he didn’t dawdle, he’d be okay.