Buthizō (βυθίζω) means to sink or submerge — to plunge something or someone into the depths. In Luke 5:7, it describes the boats filling with fish so heavily that they began to sink. In 1 Timothy 6:9, it is used metaphorically for desires that plunge people into destruction.
The terrifying metaphor of 1 Timothy 6:9 — the love of money plunging people into "ruin and destruction" — uses buthizō to paint a vivid image of spiritual drowning. What looks like gain pulls people under. Jesus walking on water and reaching out to sinking Peter (Matthew 14:30) is the anti-type: in the deep waters of life's trials, there is a hand extended to lift, not condemn.