As with all dives, divers must follow a series of steps to prepare for, plan and conduct a successful night dive:
Dive planning
When planning for your night dive, you must first determine if the environmental conditions are conducive to night diving. Night diving should not be conducted if water conditions are poor or if the weather is bad. The same conditions and situations you encounter during the daytime will be more difficult at night; do not overcomplicate your night dive by choosing to dive in less than ideal environmental conditions.
An important part of planning your dive is choosing the time of the dive. The ideal conditions for a night dive are also found immediately after sunset, the hours which change greatly from season to season: in summer, when the days are longer, it may be necessary to wait even beyond 9 PM in some parts of the world; In winter, the shorter days can allow you to enter the water even in the late afternoon (before 6 PM). This will depend on where in the world you are planning your night dives along with the season of the year.
It is recommended to have one or more qualified individuals remain on the boat, or at the entry/exit point on shore to provide surface support during the night dive. In many locations, local laws requires that at least one person remains on board the dive boat, while diving is underway, to manage the vessel and provide assistance if necessary. Surface support personnel should help the divers prepare their equipment and enter and exit the water, as well as manage the surface lights, and monitor the divers’ personal belongings.
SNSI’s recommended maximum depth for a night dive is 18 meters / 60 feet. Though, most divers stay shallower than 12 meters / 40 feet during a night dive, especially in tropical seas, as that is where most of the nocturnal life is observed. During night dives, underwater photographers usually use macro lenses in order to take photos of very small animals. In fact, many underwater photographers will stay within a 10 meter / 30 feet radius of the descent line, and shoot in shallow water. For these reasons, night dives generally have shallower maximum depths and longer dive times.
During the dive planning stage, you and your buddy should review the lost buddy procedure that you will follow in the event that one of you is separated from the other during the dive.
The suggested procedure is to first, establish neutral buoyancy, switch off your dive light and turn 360 degrees while looking for your buddy’s dive light. If you are unable to find your buddy’s dive light, turn your light back on and perform a controlled ascent. If both you and your buddy follow this procedure, you will reconnect on the surface within a few minutes. If your buddy does not surface within three to five minutes, call for help and initiate the established missing diver protocol.
Communication at night
You communicate during a night dive by making gestures with your dive light or you must direct your light to the hand which you are using to make the signals.
The following signals can be made directly with your dive light:
to make the OK signal, draw large circles with the light
to attract the attention of your buddy, move the flashlight quickly up and down
to communicate that something is wrong, move the light beam quickly from side to side
Be sure to avoid shining your light in your buddy’s eyes. If you need to get his attention, point your light at his body or make the up and down “attention” gesture with your light in front of him.
The pre-dive check
Conduct the pre-dive check with your buddy in the same manner you would for a daytime dive and pay particular attention to the equipment specific to night diving. Make sure your primary and secondary dive lights function properly. Turn on your personal beacons, make sure they are working as intended, and that they are attached securely. Finally, you and your buddy should review the underwater signals that you will use and verify what they mean.
It is a good idea not to turn on the flashlight too early before entering the water to prevent it from overheating, remember to turn it on just before entering the water. A poorly secured flashlight can fall to the bottom and is very difficult find!
Do not conduct the night dive unless you are ready and mentally prepared. Do not let anybody, including your buddy, the dive master, other divers, or the boat captain, rush you to get into the water. Nor should you rush any other person. If and when to dive is a personal decision, no one can make it for you, just as you cannot for anyone else. Do not enter the water until both you and your buddy are ready to do so.
Descending
It is highly recommended to descend using a line, separate from the anchor line, specifically for descending and ascending. As previously discussed, attach an underwater strobe light to the line.
If you do not have a dedicated descent/ascent line, you can attach a strobe to the anchor line or chain and use it as your ascent line, but be aware that the anchor line may change from taut to slack, or vice versa depending on the surface conditions.
Make a slow, controlled descent. Check your gauges often, maintain your buoyancy and use the decent line as needed. It is important to slow your descent as you near the bottom to avoid stirring up the sediment and reducing visibility.
During the Dive
During night diving it is very essential to closely adhere yo the buddy system.
Once you have reached the bottom, take a few moments to establish your buoyancy and get oriented. Look around the area and identify any natural landmarks that you can use as fixed points in combination with your compass. Diving at night is a wonderful scenario to put into practice the navigation techniques you learned in your SNSI Advanced Open Water Diver course.
In order to easily view and use the underwater compass at night, remember to make the dial fluorescent by shining a light on it for a few seconds before starting the navigation and hold the flashlight in your other hand to illuminate the path in front of you.
Natural navigation is usually more than sufficient during a night dive when you are near the bottom or watching the nocturnal marine life interact on a reef. It is truly a wonder to discover how varied and diverse the organisms are in a relatively small area. At night, each area can be very unique and most likely you will not have to travel very far from the ascent line. If you do, be sure to use your compass in conjunction with your fixed points so you can be certain of your orientation.
It is not uncommon for divers to get distracted during their first few night dives and forget to check their instruments as often as they should. For this reason, you and your buddy should remind each other to check your instruments every few minutes. Tell each other how much gas you have remaining, and if you are diving near a wall or drop off, check your computer to make sure you have not exceeded your planned depth.
Good quality gauges, such as compasses, have a fluorescent dial and it will be sufficient to illuminate them for a few seconds in order for them to remain visible for a few minutes.
The rule of thirds also applies to night dives. Use one-third of your breathing gas for the beginning of the dive, one-third for your return to the ascent point and the remaining one-third for your ascent and safety stop. Arrive at the surface with no less than 50 atm or 500 psi of gas in your cylinder. Ultimately, you are responsible for yourself. However, you and your buddy are there to lend support to each other.
During the open water night dive with your SNSI Instructor, you will participate in an exercise referred to as the “minute of darkness.” Each diver in the group will arrange themselves so that together, you form a linked circle. Once you are gathered, your SNSI Instructor will give the signal for everyone to turn off all the artificial lights, including personal beacons.
After several seconds of darkness, your eyes will start to adjust, and you will begin to see the outlines of the other divers and the surrounding area.
It is a very unique and exciting experience. If you start moving the water with your hands, due to the bioluminescence of plankton, you will be able to see bright spots all around you.
Your instructor will indicate the conclusion of the exercise by turning on his light.
Ascending & Exiting
When your dive time has come to the end, return to the ascent line and prepare to surface. Using your computer, ascend at the appropriate rate.
Avoid looking directly at the strobes as you approach them; otherwise, you risk losing your night vision. Stop for three to five minutes upon reaching your predetermined safety stop depth, usually between 3 to 5 meters / 10 to 15 feet.
Typically, a spare cylinder or, spare second stage regulators attached to long hoses, if diving from a boat, it will be located at the depth of the safety stop.
If a cylinder has been placed at the stop location, the valve will likely be closed to prevent accidental discharge. However, the second-stage regulator hoses should be pressurized to help prevent water from entering the hose.
The safety stop cylinder, or second stages from the boat should be equipped with a diffused light so they can be easily located by the divers. These safety systems should be used in the event you or another diver reach the safety stop depth with less than the recommended minimum cylinder pressure.
Return to the surface once you have completed your safety stop.
After the dive
The dive is not over upon reaching the surface. Many accidents occur after divers surface. You must remain vigilant and be attentive to your surroundings. Once you have reached the surface, keep your mask in place, your regulator in your mouth and inflate your BCD. Establishing positive buoyancy is the first thing you and your buddy should achieve.
Only turn off the flashlight once you are out of the water, but don’t keep it on needlessly “dry” to prevent it from overheating.
The dive is complete after you have returned to the boat or shore.
SNSI recommends that you log your dive as soon as possible documenting them in the MySNSI App, so that you can record your experiences as close to the event as possible. Your memories will fade over time, making it more difficult to recollect these dynamic events in the future.