The Greek bolizó means to cast a lead weight to measure the depth of water — to take soundings. It is a nautical term describing the ancient practice of dropping a weighted line to determine how deep the water is.
Bolizó appears once in the New Testament in Acts 27:28, during the dramatic account of Paul's shipwreck voyage to Rome. As the ship was driven toward shore in the dark, terrified sailors '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.' The precision of this detail — the only use of bolizó in Scripture — reflects Luke's eyewitness accuracy and the seafaring authenticity of the account. Theologically, it is an image of navigating unknown depths, which the sovereign God guides His servant through safely.