Water Entry And Descent

The divers are now ready to enter the water, where their scuba shall be given another brief inspection by their dive partners or tenders prior to descent.

7-6.1 Water Entry. There are several ways to enter the water, with the choice usually determined by the nature of the diving platform (Figure 7-8a and Figure 7-8b).

Whenever possible, entry should be made by ladder, especially in unfamiliar waters. Several basic rules apply to all methods of entry:

■ Look before jumping or pushing off from the platform or ladder.

Front jump or step-in. On edge of platform, one hand holding face mask and regulator, the other holding the cylinders, the diver takes a long step forward, keeping his legs astride.

Jon Lindbergh Diver Chicago

Rear roll. The diver, facing inboard, sits on the gunwale. With chin tucked in, holding his mask, mouthpiece, and cylinders, the diver rolls backwards, basically completing a full backward somersault.

Side roll. Tender assists diver in taking a seated position. Tender stands clear as diver holds his mask and cylinders and rolls into the water.

Front roll. Diver sits on edge of platform with a slight forward lean to offset the weight of the cylinders. Holding his mask and cylinders, the diver leans forward.

Figure 7-8a. Scuba Entry Techniques. CHAPTER 7 — Scuba Air Diving Operations

Tuck chin into chest and hold the cylinders with one hand to prevent the manifold from hitting the back of the head.

■ Hold the mask in place with the fingers and the mouthpiece in place with the heel of the hand.

7-6.1.1 Step-In Method. The step-in method is the most frequently used, and is best used from a stable platform or vessel. The divers should simply take a large step out from the platform, keeping legs in an open stride. They should try to enter the water with a slightly forward tilt of the upper body so that the force of entry will not cause the cylinder to hit the back of the head.

7-6.1.2 Rear Roll Method. The rear roll is the preferred method for entering the Figure 7-8b. Scuba Entry Techniques water from a small boat. A fully (continued). outfitted diver standing on the edge of a boat would upset the stability of the craft and would be in danger of falling either into the boat or into the water. To execute a rear roll, the diver sits on the gunwale of the boat, facing inboard. With chin tucked in and one hand holding the mask and mouthpiece in place, the diver rolls backward, basically moving through a full backward somersault.

7-6.1.3 Entering the Water from the Beach. Divers working from the beach choose their method of entry according to the condition of the surf and the slope of the bottom. If the water is calm and the slope gradual, the divers can walk out, carrying their swim fins until they reach water deep enough for swimming. In a moderate to high surf, the divers, wearing swim fins, should walk backwards into the waves until they have enough depth for swimming. They should gradually settle into the waves as the waves break around them.

7-6.2 Predescent Surface Check. Once in the water, and before descending to oper ating depth, the divers make a final check of their equipment. They must:

■ Make a breathing check of the scuba. Breathing should be easy, with no resistance and no evidence of water leaks.

■ Visually check dive partner's equipment for leaks, especially at all connection points (i.e., cylinder valve, hoses at regulator and mouthpiece).

■ Check partner for loose or entangled straps.

Check face mask seal. A small amount of water may enter the mask upon the diver's entry into the water. The mask may be cleared through normal methods (see paragraph 7-7.2).

■ Check buoyancy. Scuba divers should strive for neutral buoyancy. When carrying extra equipment or heavy tools, the divers might easily be negatively buoyant unless the weights are adjusted accordingly.

■ If wearing a dry suit, check for leaks. Adjust suit inflation for proper buoyancy.

Orient position with the compass or other fixed reference points.

When satisfied that all equipment checks out properly, the divers report their readiness to the Diving Supervisor. The Diving Supervisor directs the divers to zero their watches and bottom time begins. The Diving Supervisor gives a signal to descend and the divers descend below the surface.

7-6.3 Surface Swimming. The diving boat should be moored as near to the dive site as possible. While swimming, dive partners must keep visual contact with each other and other divers in the group. They should be oriented to their surroundings to avoid swimming off course. The most important factor in surface swimming with scuba is to maintain a relaxed pace to conserve energy. The divers should keep their masks on and breathe through the snorkel. When surface swimming with a scuba regulator, hold the mouthpiece so that air does not free-flow from the system.

Divers should use only their legs for propulsion and employ an easy kick from the hips without lifting the swim fins from the water. Divers can rest on their backs and still make headway by kicking. Swimming assistance can be gained by partially inflating the life preserver or buoyancy compensator. However, the preserver must be deflated again before the dive begins.

7-6.4 Descent. The divers may swim down or they may use a descending line to pull themselves down. The rate of descent will generally be governed by the ease with which the divers will be able to equalize the pressure in their ears and sinuses, but it should never exceed 75 feet per minute. If either diver experiences difficulty in clearing, both divers must stop and ascend until the situation is resolved. If the problem persists after several attempts to equalize, the dive shall be aborted and both divers shall return to the surface. When visibility is poor, the divers should extend an arm to ward off any obstructions.

Upon reaching the operating depth, the divers must orient themselves to their surroundings, verify the site, and check the underwater conditions. If conditions appear to be radically different from those anticipated and seem to pose a hazard, the dive should be aborted and the conditions reported to the Diving Supervisor. The dive should be aborted if the observed conditions call for any major change in the dive plan. The divers should surface, discuss the situation with the Diving Supervisor, and modify the dive plan.

Was this article helpful?

0 0

Post a comment