Many dive sites in popular areas for scuba diving have mooring balls available for dive boats to to use. These mooring balls provide quick easy access to dive sites and prevent anchor damage to sometimes delicate habitat like coral reefs. However they require maintenance and are expensive to install so not all areas divers go to will have mooring systems available. There are several other ways to secure a dive vessel over a site depending on the type of dive site, weather conditions and type of diving. Traditional anchoring, tying-in and live boating are the three different types of ways for dive boats to stay on station while divers are down.
Many new boaters greatly underestimate the importance of the correct amount of good 5/16″ chain between the line and the anchor and adequate amounts of line in the anchor locker. The general rule of thumb is that there should be 1′ of chain for every foot of the vessel’s Length Over All (LOA). The chain essentially keeps the anchor more inclined to drag across the sea floor rather than being lifted up at an angle, dramatically increasing the holding power and decreasing the scope needed to hold without dragging. Additionally the nylon line has a certain amount of elasticity which can act as a sort of shock absorber for wave action in rough seas. Another useful tool for divers to utilize when anchored over a site is a “Carolina anchor rig.” This rig essentially is a line that begins at the stern of the dive vessel descends to at least 10′ and then runs forward to the anchorline angling deeper and deeper until it attaches at around 20′. This enables divers to descend below wave action immediately upon entering the water and provides a line to pull themselves forward should surface current be too challenging or taxing. It also allows divers to spread out as they surface and decompress or complete safety stops. One last trouble saving system is the “anchor-ball” retrieval system. Essentially a large diameter buoy is attached to a steel ring that is fitted around the anchor line. When it is time to recover the anchor the vessel simply pulls forwards 30* or so relative to is bearing at anchor and the steel ring pulls the anchor vertically to the surface as the line passes through it, until the anchor is at the surface and its flukes are outside the ring. Now a crew member can simply pull in the floating anchor instead of pulling it off the bottom. This is a great system if the dive boat doesn’t have a windlass to do the heavy lifting. The only downside of this recovery system is that it shouldn’t be used if the site is a high relief wreck or reef since the lifting anchor could get snagged.
Dive boats may wish to be anchored so that the vessel is directly over the site or so that the anchor is very near the site. Anchoring over the site requires a vessel to approach from down wind/current (usually the same direction in the Gulf of Mexico). When the boat has arrived over the site the Captain should either mark the site with a jug or orient himself via the GPS Chartplotter and then pull forward 100′ to 150′ into the wind/current and drop anchor once the engines are out of gear and forward momentum has been arrested. As the boat drifts backwards toward the buoy line should slowly be paid out and some tension applied to avoid the anchor “tackle” from getting fouled upon itself. Once the anchor has set more line can be paid out to move closer to the buoy as necessary. Now divers can simply hop off the back of the boat and descend via the buoy line. This method is great for large sites that lack current. The biggest draw back to this style is that divers will lack a sturdy line to hold onto while doing a safety stop and will have to utilize the buoyancy control skills while using the line only for visual reference.
Dropping anchor near the site allows the scuba divers to use the anchor line as a sturdy descent line to the site and back to the dive boat. Adding the Carolina rig to it is ideal to combat surface current fatigue and reduce diver anxiety by getting scuba divers below the wave action and keeping them away from the bow of the dive vessel that may be bobbing dangerously (to a diver at the surface) in significant wave action. To deploy the anchor near the site it is easiest to motor into the wind/current until the desired site shows clearly on the bottom machine and then take the boat out of gear. As the current pushes the boat backwards away from the site the anchor should be dropped shortly after the site is no longer showing on the bottom machine. Now as divers descend to the site it will appear in front of them, and should it not be immediately at the anchor it will be a short swim in the same direction forward. This system of anchoring is preferred if you must anchor in challenging conditions or heavy current since divers who may not find the anchor before needing to ascend. They should surface in front of the boat and the current will simply bring them to the back of the boat. The downside of anchoring with either system is that conditions can change such as currents or wind switching directions and thus moving the anchor-line and boat relative to the site. Even worse, sometimes anchors simply drag due to loose sediments or not enough sediments and diver may return to where the anchor was only to see a drag line in the sand!
The solution to anchor drag is a “tie-in” system whereby the site becomes the anchor. To “tie-in” a dive boat will need an experienced diver, 10-15′ of chain and an anchor line at least twice as long as the site is deep with a buoy on the opposite end as the chain. The boat motors into position over the (again into the wind/current) shipwreck or artificial reef where the chain can be wrapped around a sturdy point and tied into a binding knot. The diver splashes in, finds the correct tie-in point and secures the line to the site. At this point either a tug system can be used to tell the line tender that the knot is tied or the whole line is already thrown off the dive boat while it stands off a safe distance awaiting the diver’s return to the surface near at the buoy. While this system requires an experienced diver who may have to burn some dive time working (someone will have to untie too) it is the most secure way to provide an absolute line to the wreck that will not drag. In strong current a Carolina rig can be applied to this system as well. Less scope is needed for this method of staying over a dive site and multiple boats can tie-in to the same wreck at the same time provided they have adequately communicated to each other, where as you cannot drop an anchor on a dive site if divers are in the water already. This is the method dive charters in the Northern Gulf use on popular wrecks to maximize safety and share the sites with others.
One last method to put divers on a site is to not anchor at all but to rather “live boat.” Live boating is preferred for large sites, drift dives, and coral reefs without mooring systems. Essentially the boat simply pulls over the site or up-current of the site and the divers enter negatively buoyant and descend in a rapid but controlled manner. A marker buoy can be used as a visual aid to the boat and divers as long as the site isn’t in danger of being damaged by its heavy weight. Divers can either drag a surface flag or carry inflatable Surface Marker Buoys and audible signals such as a storm whistle or Dive Alert. Divers are free to swim where they will under this non-anchoring system, without being burdened with a line to keep track of. Live boating is preferred where divers will need to cover a lot of ground or may have limited bottom time. Dive operations off the SE coast of Florida commonly employ this method due to the high current there. Divers will need to be more competent in this method and carry more gear but they enjoy greater freedom during the dive. The dive vessel will need to carefully follow the bubbles and vigilantly watch for surfacing divers.
In summary there are numerous ways to get scuba divers from a dive vessel to a site and back again. Conditions, the nature of the dive site, and the skill of the divers will ultimately dictate how the vessel should be holding station.