Downcurrent

A current flowing downward along a wall or slope that can drag divers deeper; countered by swimming out horizontally and adding buoyancy.

A downcurrent is water flowing downward, usually where a horizontal current hits a wall, drop-off, or pinnacle and is deflected down the face. Divers who have met one describe it as an underwater waterfall: your bubbles travel sideways or down, your depth gauge unwinds, and finning upward achieves little. Strong downcurrents exist at famous wall sites in Cozumel, Komodo, and the Galapagos.

The escape is horizontal, not vertical. Swim perpendicular to the wall, out into open water, because downcurrents are usually narrow and hug the face; a few meters out, the flow weakens or stops. Add air to your BCD to fight the descent, but be ready to vent aggressively the moment you exit, since you will be overweighted for the calm water. Never ditch weights at depth in panic. Grabbing bare rock to arrest a drop is acceptable in a genuine emergency.

Watch for warning signs in the briefing and in the water: current lines converging on a point, bubbles streaming down, or fish oriented nose-up and working hard. Monitoring your depth and ascent rate closely is what turns a downcurrent from a story into a footnote. If your computer alarms on descent speed, act immediately rather than waiting to see what develops.