https://www.wired.com/story/floating-metal/

A great way to anger the gods is to call your ship unsinkable. People thought the Titanic couldn't go down, and as Kate Winslet and Leonardo DiCaprio found out the hard way, that clearly wasn't the case. (Leo himself was also, in fact, quite sinkable.) But at the University of Rochester, scientists have defied the gods and created a clever, simple device that seems to indeed be unsinkable, at least in the lab.

Using an absurdly powerful laser, the researchers etched fine patterns into the metal, which trap air. By sandwiching two of these pieces of metal together with etched sides facing in, yet leaving a gap in between, they can capture a bubble of air in the center. Drop the sandwich in a tank of water and it does something very unbecoming of metals: It floats no matter what. Even when the researchers forced the device to the bottom of the tank and held it there for months, it still surfaced when they let it.