Tides and currents

The tidal range around One Tree Island can be up to 3.5 metres and strong currents are associated with these spring tides. Tidal variation during the lunar cycle can influence the accessibility of research and dive site within the lagoon and access to the reefs edge. It is recommended that you consult with the Station Managers to ensure the best dates for your boating activities. Tide tables for One Tree Island are available here [link to tides] and also from the station managers. Tide tables must be consulted prior to any diving or boating operations taking place. Divers, Snorkellers and Boat Operators must always check the current strength and direction before entering the water, and anticipate any increase in current flow or change in direction.

Dive coordinators and leaders must be aware of precautions that must be exercised with regard to currents. Prior to entering the water the Dive Coordinator, Dive Attendant / Boat Person and dive team must discuss the rescue procedures to be followed; should one or more divers be caught in a current whilst other divers are still underwater / on-site. Diving in currents demands an extra level of fitness and divers must pay particular attention to their air supply, as air consumption can be dramatically increased due to the extra exertion involved in diving in currents:

  • Diving in currents stronger than a diver can easily swim against is strongly discouraged.
  • All divers involved in diving in strong currents must be experienced in this type of diving and be tethered to the boat or use a surface float so their location is always visible.
  • An experienced boat handler with knowledge of local conditions must be in charge of the vessel.
  • Where an anchored vessel is being used for untethered SCUBA operations in strong currents, a float line must be used by all divers and a current line of at least 30 metres length and 10 mm diameter must be streamed behind the vessel.
  • The divers must only work 'up-current' of the vessel, and must remain in buddy contact.
  • It is strongly recommended that divers descend and ascend along the anchor line.
  • A diver on the surface caught in a current downstream of the dive boat's current line, should remain calm, and fully inflate their BCD and their surface signalling device. A whistle should also be used to attract the Dive Attendant's attention.

Underwater visibility in the lagoons and around the outer reef edge may be dramatically reduced with ebbing tides, to less than 2 metres. This should be considered before every dive. Measures should be considered and taken if necessary, prior to any dive, which may assist divers to operate in poor visibility.