Read Acts 27:28 Using Other Translations
And sounded, and found it twenty fathoms: and when they had gone a little further, they sounded again, and found it fifteen fathoms.
So they took a sounding and found twenty fathoms. A little farther on they took a sounding again and found fifteen fathoms.
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.