William Ferrel: introduced significant wave" forecasting

measured under-surface currents using a current drag

created a tide-prediction machine

developed the first sonar device

William Ferrel created a tide-prediction machine.

Explanation:

William Ferrel create a machine in late 19th century that was the best combination of mechanical parts and computer coding. It was a mechanical analog computer that could predict the ebb of tides and even the height of tides that could be irregular. It was widely used for marine networks and navigation. Later on many improvisations and additional features were added on it. During the world war times, this tide prediction machine was of great use for military purpose.