What Keeps a Ship Stationary in the Ocean?

**Nothing keeps a ship perfectly still** on the open ocean. A vessel underway drifts with currents, waves, and wind (leeway). To maintain position, ships use:

• Anchoring: Only in shallow water (< 80 m typically); anchor + chain catenary holds position but vessel swings in circle (swing circle radius = 3–5 × depth). Still moves with waves (surge, sway, heave).
• Dynamic Positioning (DP): Thrusters (bow/stern/azimuth) + GPS/gyro/MRU sensors hold position/heading automatically. Used by drillships, offshore vessels, cruise ships in tender ports. DP Class 1/2/3 redundancy.
• Mooring: To buoy, dock, or seabed anchors (spread mooring); limits motion but not eliminated.
• Drifting / Hove-to: Engine minimum, bow into seas; slow drift.

Key Point

Even "stationary" ships move—**six degrees of freedom** (surge, sway, heave, roll, pitch, yaw). True stillness is impossible in a fluid medium. Anchored ships drag in storms; DP consumes fuel; mooring lines fatigue.