They took SOUNDINGS and found that the water was a hundred and twenty feet deep

[tonychanyt]

Acts 27:28

They took soundings and found that the water was a hundred and twenty feet deep. A short time later they took soundings again and found it was ninety feet deep.

Thayer's Greek Lexicon

STRONGS NT 1001: βολίζω​

βολίς a missile, dart; a line and plummet with which mariners sound the depth of the sea, a sounding-lead); to heave the lead, take soundings:​

How did they take soundings?

New Living Translation:

They dropped a weighted line and found that the water was 120 feet deep. But a little later they measured again and found it was only 90 feet deep.

Etymology:

The word “sounding,” meaning the measurement of water depth, comes from an Old English word meaning water or sea and has nothing to do with audible sound.​