Dan Lasko, a former United States Marine who's had one of his legs amputated, never thought he'd be able to swim the way he used to—until coming across "The Fin." The Fin is a 3-D device that attaches to prosthetic legs, helping people to swim.

Dan Lasko, a former United States Marine who’s had one of his legs amputated, never thought he’d be able to swim the way he used to—until coming across “The Fin.” The Fin is a 3-D device that attaches to prosthetic legs, helping people to swim.