Currents and Drift Diving Technique

Current as a Feature, Not a Problem

The relationship between divers and current changes as experience accumulates. Beginners learn to check current and, when possible, avoid it. Intermediate divers learn to dive at slack water. Advanced divers learn to use current as the most powerful tool in underwater exploration — it brings food, concentrates marine life, and carries you effortlessly through diving's most spectacular landscapes.

The famous sites — Blue Corner in Palau, the Maldivian channels, Komodo's Castle Rock, the Galapagos — all run with significant current. The current is not incidental to what makes these sites special; it is the specific cause of the marine life concentrations.

Types of Current

Tidal current — the most predictable type — flows in response to the gravitational pull of the moon and sun. In channels and passes between bodies of water, tidal current reverses direction twice daily (in semidiurnal tide patterns). The current speed peaks at mid-tide and drops to near-zero at high and low tide (slack water).

Density current drives water of different temperatures or salinities past each other — common in areas of upwelling. In Komodo, these upwellings are the cause of both the cold water and the extraordinary plankton productivity.

Down-current — water flowing downward at reef edges and pinnacles — is the most dangerous current type for divers. A down-current can exceed the diver's ability to ascend. Emergency procedure: if caught in a down-current, swim horizontally off the reef into open water, inflate the BCD, and ascend in the open water away from the reef structure.

Reading Current Before Entry

A divemaster who knows a site can assess current from the surface:

• Mooring line angle: If the boat's mooring line angles away from vertical, current is running.
• Surface debris: Floating leaves and foam show surface current direction and speed.
• Ripple texture: On calm days, areas of surface turbulence indicate upwellings or eddies.

Drift Diving Technique

In a drift dive:

• Do not fight the current. Use it. Position yourself to move with it, hover neutrally buoyant, and allow the reef to pass you.
• Maintain group contact. In current, separation happens fast and recovery is impossible.
• SMB readiness. Every drift diver must carry and be able to deploy a surface marker buoy at depth. This is the primary recovery tool when a drift ends away from the boat.
• Ascent planning. At the end of a drift, you may need to ascend in open water without a descent line. Exhale slowly, control ascent rate (max 9 metres per minute), pause at 5 metres for 3 minutes safety stop, then deploy SMB before surfacing.