There are essentially two types of dives conducted from boats. Dives from an anchored boat, and drift dives while the boat is in motion, each of which has specific procedures. The intensity of existing currents and the desired distance to be covered are the two main deciding factors when choosing between diving from a fixed position, or a drifting boat. If the dive site is relatively small, for instance when diving on a wreck or on a reef with little to no current, then diving from an anchored position is ideal. Some popular dive sites in this category have permanent moorings with surface buoys in place for boats to attach to so that they do not have to drop anchor each time they visit the site.
Divers will need to use navigation techniques in order to return to the ascent line when diving from a moored boat. If there is a current present, the dive should start into the current. When the predetermined dive time has passed, or the first third of gas has been consumed, the team should return to the ascent point by turning and swimming with the current.
When the current is too strong to swim against, a drift dive will be conducted. In this scenario, the dive team will enter the water, descend and drift with the current until the time comes to ascend. In some cases, the boat will be anchored at the start of the dive and will travel to the planned exit area after the last dive team has entered the water. In this type of dives, every diver should carry a surface-signaling device in order to signal the boat after reaching the surface. Some dive boats specify what type of signaling device they require, and may supply them to the dive teams. Be sure to find this out before you depart. Once you reach the surface after the dive, inflate your BCD so you float comfortably, activate your signaling device, and wait for the boat to arrive. If you ascend near shallow reef formations or other obstacles, you may need to swim to a deeper location where the boat can approach without the threat of collision. Keep your mask and regulator in place as the boat approaches. The boat’s engines will be running and removing your mask or regulator would expose you to the noxious exhaust fumes. When possible, wait until you are safely on board before removing the mask or regulator. If the boat is equipped with tubular steps, it may be possible to climb to the deck with your fins on. If not, you may need to remove your fins and hand them to deck personnel before climbing up.
When waves are present you will have to remove your fins by holding on to the surface safety line, put the fin straps over your hands (wrists) and once it is your turn, you will approach the ladder and be ready to climb quickly.
When the boat is unable to anchor, divers will enter the water according to the guidelines of the boat’s commander. Typically, all of the divers that will participate in the dive must be ready to enter at the same time.
When the boat is in position and the dive teams are ready, the commander will signal the divers to enter the water. The divers regroup on the surface and descend as a unit. In strong currents, it may be necessary to descend immediately after entry in order to preserve as much dive time on the site as possible. The exit procedures for this type of dive are the same as those described above.
Drift diving is a wonderful way to explore a large swath of reef in a relatively short amount of time. However, divers must be prepared and properly equipped and weighted before the dive begins. Once in the water, there are very few options to correct issues without terminating the dive. It is best to gain experience drift diving in slower, more relaxed currents, and build up to faster and stronger currents as your comfort level increases. Most dive boat operators will have different drift dives planned for divers of various experience levels.