13.0 GENERAL

Diving from surface support platforms can be grouped generally into the following categories:

a. From the shore

b. From a pier or stationary platform c. From a small boat

d. From a ship.

The following discussions give some characteristics of each and some general guidelines to follow.

13.1 DIVING FROM THE SHORE

A diver can expect to encounter a wide variety of conditions when entering the water from the shore. Shorelines vary greatly, and diving from a particular one will require individual preparation and planning.

Prior to entering the water from the shore, special attention should be given to the predive equipment checkout. As diving equipment quite probably will be placed on the ground near the water, small dirt particles could enter an area where a perfect seal or close tolerance is required. Even the smallest amount of dirt in the regulator or reserve valve could cause a serious air leak or the valve to malfunction. Extra care must be taken to ensure that diving equipment is kept as free from dirt as possible.

If the dive from shore is to be made at a precise underwater location, it is advisable to clearly mark the spot at the water surface. This can be done by using a marker buoy or surface float. A small marker buoy floating on the surface can be difficult for a diver to see. Compass bearings, underwater contours or features, or triangulation methods with known. shore positions can help in initially locating a dive spot.

When diving from the shore without a boat, the use of a surface buoy or float with a diving flag to indicate divers below is recommended. If entry conditions permit (surf, etc.) divers should carry

and/or tow the marker with them to the dive site. It is also advisable that each diver be equipped with a day/night signal flare for signaling the shore in an emergency. They provide a quick means for accurately locating a diver on the surface.

Entering the water from a smooth, unobstructed shoreline where the water is relatively quiet should pose no problems. Most lakes, rivers (where currents near shore are not swift), bays, lagoons, quarries, and ocean coastline where surf is negligible, fall into this category.

13.1.1 Through Surf

Entering the water through even moderate surf, burdened with diving equipment, is a difficult and potentially hazardous operation. A careful analysis of surf conditions should be made, and, if conditions are considered too severe to allow safe passage to open water, the dive should be terminated.

WARNING

Before Attempting to Dive Through Surf on an Unfamiliar Beach, Consult Local Divers Concerning Surf Conditions.

Time should be taken prior to entering the water to observe the surf. As swell, waves traverse vast expanses of ocean with little modification or loss of energy. However, as the waves enter shallow water, the motion of the water particles beneath the surface is altered. When the wave enters water of depth equal to or less than one-half the wavelength, it is said to "feel bottom." The circular orbital motion of the water particles becomes elliptical, flattening with depth. Along the bottom, the particles oscillate in a straight line parallel to the direction of wave travel.

As the wave "feels bottom," its wave length decreases and steepness increases. Furthermore,

as the wave crest moves into water where the depth is about twice that of the wave height, the crest changes from rounded to a higher, more pointed mass of water. The orbital velocity of the water particles at the crest increases with increasing wave height. This sequence of changes is the prelude to the breaking of the wave. Finally, at a depth of approximately 1.3 times the wave height, when the steepest surface of the wave inclines more than 60 degrees from the horizontal, the wave becomes unstable and the top portion plunges forward. The wave has broken; this is surf (Figure 13-1). This zone of "white water," where the waves finally give up their energy and where systematic water motion gives way to violent turbulence, is the surf zone. The "white water" is a mass of water with bubbles of entrapped air.

Having broken into a mass of turbulent foam, the wave continues landward under its own momentum. Finally, at the beach face, this momentum carries it into an uprush or swash. At the uppermost limit, the wave's energy has diminished. The water transported landward in the uprush must now return seaward as a backwash, or current flowing back to the sea. This seaward movement of water is generally not evident beyond the surface zone or a depth of 2-3 feet (Somers 1972).

By watching the surf for a short period of time. water entry can be timed to coincide with a small -et of waves.

When ready to enter, approach the water, fully dressed for diving. When reaching the water's edge, spit on the faceplate, rinse and adjust to face, and place snorkel in mouth. Turn around and back into the water. Knees should be slightly bent and the diver should lean back into the wave with one hand on the faceplate. If conditions are good, begin swimming seaward on the surface using a snorkel. If heavy sets are encountered, it may be necessary to switch to scuba.

WARNING

If a Diver Inhales at the Same Time a Trough Passes Overhead, It May Have the Same Effect as Inhaling While Ascending and Could Cause an Embolism.

Swimming over breakers should not be attempted. As they approach, duck the head and dive into and through them.

Once safely through the surf, check all equipment. Even a moderate surf can knock equipment out of adjustment or tear it away.

Sand in the mask, regulator, or fins may be found after passing through surf. Take time to remove it prior to continuing the dive. Sand in the exhaust valve of a regulator can cause it to seal improperly and water, as well as air, may enter the mouthpiece when inhaling. Sand in the fins, while only mildly

irritating at first, can cause a painful abrasion by the end of a dive.

Exiting from the water through the surf is basically the opposite procedure from entering. Wait just seaward of the surf for a small set of waves. When a set is selected, begin swimming shoreward immediately after the passage of the last of the larger waves. The smaller waves breaking behind will assist in progress toward the beach. Using this assisting wave action, swim toward the beach until in approximately waist-deep water. At this point, while there is still enough water for support and balance, pivot around, face the waves, and plant the feet firmly. Stand up, and bending enough to maintain balance, back out of the water. As soon as the surf is cleared turn and remove fins. If knocked over by surf action after standing up, do not try to stand again. Let the waves carry you onto the beach. Dig hands and fins into the bottom to prevent being swept seaward by the backwash. Crawl out of the surf on hands and knees.

13.1.2 Surf on a Rocky Shore

Prior to entering surf from a rocky shore, evaluate the wave conditions. Do not attempt to stand or walk on rocks located in the surf zone. A knock down can be hazardous. Select the backwash of the last large wave of a series, and enter the water. The backwash should carry through the rocks. Maintain a prone swimming position and face the next oncoming wave. Grasp a rock or kick to keep from being carried back toward the shore. Then kick seaward after the wave passes.

When exiting on a rocky shore, stop outside the surf zone and evaluate the wave conditions. Exit toward the beach on the backside of the last large wave of a series. As momentum from the wave is lost, grasp a rock or kick to avoid being carried seaward by the backwash. Maintain position, catch the next wave, and move shoreward. Exercise caution moving over slippery rocks.

13.1.3 From a Coral Reef

Diving operations from a reef should be planned, if possible, at a high tide when water covers the reef. For a diver with equipment on, walking on a reef is hazardous. Footing is uncertain, reefs are generally pocked with holes, and areas that look solid may break under a diver's weight.

NOTE:

Coral Shoes or Hard-sole Neoprene Boots Should Be Worn Around Coral.

In some instances, an area may be encountered on the shore side of the reef where water is deep enough for swimming. In this case, the outer side of the reef will break up the wave action sufficiently to allow passage over the inside, calm area without trouble. If a channel can be located which will allow passage through the reef, follow it, submerged if possible, into deep water. If a satisfactory passage cannot be located, approach the edge of the reef, wait for a wave to pass, and slip over.

13.2 DIVING FROM A PIER OR

STATIONARY PLATFORM

Diving from a pier or platform rather than directly from the shore offers many advantages. Entry into deep water can be made without having to traverse a surf line, rocks, or other obstacles. Also, if the dive site is under, or in proximity to the pier, the use of surface-supplied diving equipment can be considered. Usually, all required equipment can be transported directly to the dive site by vehicle.

Ladders should be used to get down as close to the water as possible before entry. Any of the approved entry techniques, such as stepping in or rolling in can be safely used for heights of up to 10 feet. Immediately prior to entering, carefully check for floating debris or submerged obstructions. Floating debris is common around a pier, and pilings normally rot or break off just below the waterline.

Once in the water, swim to the dive site on the surface, if the site is relatively close to the pier or platform. If the dive site is a significant distance, the use of a small boat is advisable.

When it is required to swim under a pier or platform, do so submerged, whenever possible. Under water a diver has more control of his movements and rough contact against pilings, cross-supports, and other potentially hazardous objects is more easily avoided.

When exiting the water onto a pier or platform, stop at the ladder and remove fins. (The ladder, ideally, should extend 3 to 4 feet into the water.) Climbing a ladder with fins is awkward and dangerous, and should be avoided. Tanks and other cumbersome equipment should also be removed and tied securely to a line dropped from the top.

13.3 DIVING FROM A SMALL BOAT

The small boat is probably the most common surface support platform used by divers using self-contained equipment. Configurations and types vary greatly and run from small, inflatable boats to larger solidhulled vessels (See Figure 6-4).

In planning a dive using a small boat as a platform, the following characteristics should be considered. The boat:

a. Should provide a means for divers to easily and safely enter and leave the water.

b. Must be seaworthy and not loaded beyond the capacity recommended by the manufacturer for the expected water conditions.

c. Must be large enough to adequately accommodate all members of a dive party, the diver's life-support equipment, and any special equipment being used in support of the dive.

d. Should provide some means of shelter in cold and/or inclement weather for the dive party while going to the dive site and, most importantly, for the divers after they leave the water and are returning to shore.

e. Must be properly maintained and in good repair.

f. Must be maneuverable if it is to be used as a pickup boat.

g. Must carry a diver's flag.

13.3.1 Entering the Water

Entering the water can be safely accomplished from a small boat by several methods. Sitting on the gunwale and rolling into the water is considered best (Figure 13-2). Sit on the gunwale facing the center of the boat with both feet inside. Extend as much of the body as possible over the water while leaning forward to counterbalance. When ready to enter simply sit up, lean backward, and let the weight of the diving equipment carry you back over the side. A second method of entry is the "step-in" method and is normally used when entering the water from a larger boat. Step on to the gun