After locating the object of
your search, if it is small enough, an immediate retrieval and
recovery can be initiated. It is a good idea to carry a mesh type
"Goodie Bag" to assist in transporting the object to the surface.
However, should the recovered object be of evidentiary value in
court, special handling may be required. Larger objects will require
that additional measures be taken. It is recommended that a marker
buoy be attached to the object prior to beginning recovery. This
will serve to accomplish two things:

1) Your surface support will
be aware that you have located the object, and;

2) Should you later lose
sight of the object, you will avoid repeating the search. (There
have been instances wherein divers located an object, failed to
mark it, lost it, and were unable to locate it again to recover
it).

Plan ahead with respect to the
mode of recovery to be used. Decide what you will do with the object
once it is at the surface. Depending upon the size of the object,
you may have to use either an apparatus to buoy the object to the
surface or alternatively a surface line secured to the object. The
use of a surface line is probably the safest method, however, a
surface line requires the use of a watercraft capable of carrying
the added weight of the object. Either block and tackle or a power
winch system can be used. As a precaution, it would be best to first
ascertain the weight of the object (out of water) to ensure that the
lifting apparatus and it's mounts are sufficient in strength to
handle the load. There are several cases on record where would-be
salvers have "winched" the stern transom right off their boat, or
instead of hauling an object up, have pulled the bow of their vessel
underwater, which resulted in a new dive site for the wreck diver or
underwater photographer.

Inflatable devices are the most
commonly used and most practical method of underwater recovery. This
technique involves attaching containers to the object to be raised,
then filling them with air until the positive buoyancy of the
container equals the negative weight of the object. The object will
then rise to the surface. Although commercial lift bags and
55-gallon drums are commonly used for this type of recovery, any
number of devices may be used including air spaces or inflatable
compartments in the object itself. One must take care, however, to
ensure all lifting devices be equipped with either a line or chain
strong enough to handle a load of at least three times the lift

capacity of the device. When
using a lifting device be sure to choose an appropriate one for the
size of the object.

A fairly common mistake made by
novice salvers is to attempt to "ride" the lifting device either
during descent or ascent. This is extremely dangerous and can cause
serious injury or death to the rider. During a descent, divers who
attempt to ride a device to the bottom can rupture eardrums or
sinuses, due to inability to equalize during the rapid descent. In
addition, the diver can become entangled in the chain or line, which
can cause injury or damage to diving equipment. During the ascent,
an embolism could occur due to expanding air in the lifting device
causing rapid acceleration toward the surface. Avoid an uncontrolled
lifting ascent by bleeding air from the lift bag dump valve or
"burping" the bag during ascent.

Overfilling a lift device can
also be extremely dangerous. An out of control device might break
the surface, rise completely out of the water, dump its air, and
cause the object to descend rapidly, which could strike or pin any
diver beneath the object to the bottom. It is generally better to
use two smaller devices as opposed to one large one. Prior to
commencement of filling the lift device(s), clear the area above and
around the object. Leave a marker buoy attached to the object, in
the event that during ascent, should the object "break loose" it can
be easily relocated. Once the lift device begins its ascent with the
object, clear the area below the object.

In order to lift an object, the
size and weight of the object to be raised must first be determined.
This can generally be ascertained by checking known sources. For
example, if a diver is interested in raising an outboard motor,
check with a local dealer, manufacturer's representative, or find a
similar article and check its weight. For an "on the spot" salvage
attempt, however, a different method of determining the approximate
weight will need to be applied.

1) Simply make a "blind
guess" at the approximate weight, and then provide extra
flotation equipment to over buoy the object.

2) Calculate the weight by
using a basic formula: Weight = (volume) (specific weight).

As an example: If it is
known that the specific weight of iron is 490 pounds per cubic
foot, and estimate that the iron object you wish to lift
contains a total of 3 cubic feet of material, then ...weight =
(3 cubic feet) times (490 pounds) = 1,470 pounds gross weight.

Engineering manuals are
available that list the specific weights of materials; and if the
approximate size of the object can be determined in terms of a cubic
measurement, the approximate weight of any object can be determined.
You can then concern yourself with the device(s) necessary as a
lifting force.

Assume that you have located a
section of steel pipe that you wish to raise, and the estimated
weight of this pipe is 850 pounds. The question would now be, "How
many 55-gallon fuel drums will be needed to effectively lift this
pipe section to the surface?"

There is one other piece of
information needed to solve this problem: the depth of water from
which the pipe is to be raised. As the depth (pressure) of the water
will have a direct bearing on the volume of gas required to fill the
lift device to positive lifting capacity.

You find, as an example, that
one (1) 71.2 cubic foot cylinder compressed at 2,475 p.s.i. (2250 +
10%) will completely fill nine and three fourths 55-gallon fuel
drums at the surface. This same cylinder will only fill four and
seven-eighths drums at a depth of 33 feet, (sea water). A 55-gallon
drum contains 7.33 cubic feet of gas at sea level.

To calculate the volume required
for lifting devices, use the following formula:

Number of gallons capacity -
7.5 (the number of gallons in a cubic foot) = cubic feet of air
contained.

To determine the gas
requirement "at depth", apply
Boyle's Law to the cubic
feet of gas required at the surface.

Now that you can calculate the
amount of gas required to fill a given device, how do you determine
the actual lifting capacity of that device? To begin, one cubic foot
of air will lift 64.2 pounds of dead weight in sea water. A cubic
foot contains approximately seven and one half (7.5) gallons. One
gallon of air will lift eight and one half (8.5) pounds of dead
weight in sea water. There are 1,728 cubic inches in a cubic foot.

One cubic inch of air will lift
approximately four one hundredths of one pound (.0372) of dead
weight in sea water. One cubic foot of air will lift 62.5 pounds of
fresh water, 3 percent less.

With the 55-gallon fuel drum as
an example, you can figure an approximate lift capacity of just
under 420 pounds. To arrive at a lift capacity figure for any given
container, you must have the following figures:

1. The liquid capacity of
the container (expressed in gallons);

2. The fact that one (1)
cubic foot of liquid = 7.5 gallons;

3. The specific weight of
water (62.4 pounds per cubic foot for fresh water and 64.2
pounds per cubic foot for sea water);

4. The weight of your
container (weight at surface).

With this information, you can
now supply the following formula:

L.C. = (V) - (7.5) X (ws
fluid weight) - weight in air.

In this formula, we find that
L.C. = lift capacity, (V) = volume (in gallons of liquid) of the
lift device, (7.5) = the figure used to convert "gallons of liquid"
into cubic feet (since cubic foot is equal to 7.5 gallons), ws fluid
- the specific weight of water (62.4 pounds per cubic foot for fresh
water and 64.2 pounds per cubic foot for sea water) and weight in
air minus the weight of our container when it is weighed empty at
the surface. (The weight of the average 55-gallon drum is 53
pounds).

If you now put this formula to
work, you find that L.C. = (V) gallons - (7.5) X ws fluid) minus 53
pounds. So the lift capacity of the 55-gallon drum is found to be
approximately 418 pounds in sea water (408 pounds in freshwater).

Returning now to the
hypothetical salvage problems of the 850 pounds section of pipe, you
find that we will need two (2) 55-gallon drums, and that at a depth
of approximately 33 feet in sea water you will need slightly less
than the contents of one half of a standard diving cylinder (71.2
cubic feet at 2,475 p.s.i.).

When deciding on the lifting
device to be used for any particular salvage attempt, one must keep
in mind the fact that if the device is filled with compressed air
"at depth" that volume of compressed air is going to expand as the
device ascends to the surface (Boyle's
Law). With this in mind, one must be certain that
the expanding air can escape, or the lift device may rupture before
it reaches the surface.

This "venting" or escape of air
can easily be provided for by leaving the openings or plug out
during the ascent, and then inserting the plug at the surface.

The reason more lifting devices
are not needed is because there is a specific gravity differential
between the sea water and the steel pipe of 64.2 pounds per cubic
foot of steel, which must be subtracted from the weight of the steep
pipe in salt water.

So assuming the steel pipe
contained approximately 2 cubic feet of steel at 450?? pounds
per cubic foot, on the surface it would only weigh 772 net pounds in
sea water....Archimedes
Principle.

A sinking object will displace
its material mass or size in a liquid. The amount displaced is a
working force that can be deducted from the material weight of the
item in a liquid when determining the lifting force necessary to
make buoyant that sunken object. But to lift the object from the
sea, the lifting device used in this case should be designed to
handle the surface weight of the object.

Do not partially fill a
container! Fill each container totally, starting with the smallest
and finishing with the largest.

Install the largest lift in the
center and balance lift from both ends. Tie a bowline onto the
container and a double turn and two half hitches to the item to be
lifted.

Tie downs can be attached to a
lift device by using thick netting, cable, or ropes tied around the
outside. However, a much simpler and easier method is to weld chain
to a piece of angle iron or strap iron of dimension that will allow
the strap to slip into the mouth of the 2-inch bung. Insert the
strap iron in the bung and it will turn crosswise in the inside of
the barrel with the chain and tie-on ring extending below barrel, to
be used to attach the object desired to be lifted. This method is
secure and will allow barrels to tilt as necessary with very little,
if any, loss of air.

The most useful knot for tie-on
lines underwater is the bowline. It holds fast, and is easy to untie
later.

**
****FIGURES & FORMULAS PERTINENT
TO SEARCH & SALVAGE**

- A cubic foot of salt water
weighs 64.2 lbs

- A cubic foot of fresh
water weighs 62.4 lbs

- 1,728 cubic inches equals
1 cubic foot

- 1 Gallon weighs 8.5 lbs in
seawater (indicates the lifting ability of air)

- 1 cubic foot is equal to 7
1/2 gallons of lifting capacity

- 1 gallon will lift 8 1/2
pounds

- 1 cubic inch of salt water
weighs 0.0371 pounds per cubic inch

- 1 cubic inch fresh water
weighs 0.0361 pounds per cubic inch

- Volume of a cube = width X
height X depth

- Formula for determining
the lift capacity of an inner tube in ocean:

D = Diameter

(0.7854 X D X NC) X 0.371)

NC = Neutral Circumference

- Formula for the lifting
capacity of a cylinder:

L = Length

(0.7854 X D X L) X 0.0371

(Gives lift in salt water less
the weight of the container).

- Formula for lifting
capacity of a sphere:

(0.5236 X D ) X 0.0371

- Gallons divided by 7.5 =
cubic ft Air

- 1 ea 72 cubic ft tank
w/2150 PSI fills 7 ea 55 gallon drums at sea level or 2 & 1/3
drums at 100 feet

- 1 ea 71.2 cubic ft tank at
2250 PSI = 10 @ 70 degrees F. will fill 9 3/4 (55 gallon) drums
@ sea level and 4 7/8 drums @ 33 feet (ocean)

- 1 ea 55 gallon drum lifts
420 lbs (less weight of drum)

- 55 gallon drum holds 7.35
cubic foot air at sea level

(Lift capacity) LD =__ (V)__
X ws fluid = (weight in air)

L.C. = Lift Capacity

V = Volume (in gals liquid of
lift device)

7.5 = Gallons of liquid (cubic
feet)

ws fluid = Specific weight of
water (salt vs fresh)