Question: What should be done to adjust a boat's landing in order to change it's fore-and-aft attitude while in the water?
About the article "Sailing", section "Hull trim".

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Hull trim is the adjustment of a boat's loading so as to change its fore-and-aft attitude in the water.
In small boats, it is done by positioning the crew.
In larger boats the weight of a person has less effect on the hull trim, but it can be adjusted by shifting gear, fuel, water, or supplies.
Different hull trim efforts are required for different kinds of boats and different conditions.
Here are just a few examples: In a lightweight racing dinghy like a Thistle, the hull should be kept level, on its designed water line for best performance in all conditions.
In many small boats, weight too far aft can cause drag by submerging the transom, especially in light to moderate winds.
Weight too far forward can cause the bow to dig into the waves.
In heavy winds, a boat with its bow too low may capsize by pitching forward over its bow (pitch-pole) or dive under the waves (submarine).
On a run in heavy winds, the forces on the sails tend to drive a boat's bow down, so the crew weight is moved far aft.
A typical manned torpedo has a propeller and hydroplanes at the rear, side hydroplanes in front, and a control panel and controls for its front rider.
It usually has two riders who sit facing forwards.
It has navigation aids such as a compass, and nowadays modern aids such as sonar and GPS positioning and modulated ultrasound communications gear.
It may have an air (or other breathing gas) supply so its riders do not have to drain their own apparatus while they are riding it.
In some the riders' seats are enclosed; in others the seats are open at the sides as in sitting astride a horse.
The seat design includes room for the riders' swimfins (if used).
There are flotation tanks (typically four: left fore, right fore, left aft, right aft), which can be flooded or blown empty to adjust buoyancy and attitude. 
Small airships carry their engine(s) in their gondola.
Where there were multiple engines on larger airships, these were placed in separate nacelles, termed "power cars" or "engine cars".
To allow asymmetric thrust to be applied for maneuvering, these power cars were mounted towards the sides of the envelope, away from the centre line gondola.
This also raised them above the ground, reducing the risk of a propeller strike when landing.
Widely spaced power cars were also termed "wing cars", from the use of "wing" to mean being on the side of something, as in a theater, rather than the aerodynamic device.
These engine cars carried a crew during flight who maintained the engines as needed, but who also worked the engine controls, throttle etc., mounted directly on the engine.
Instructions were relayed to them from the pilot's station by a telegraph system, as on a ship.
While elevators and swivelling propellers provide fine control of altitude, larger changes of height used to be controlled by either venting gas to lose altitude or dropping ballast to gain altitude.
Large airships typically carried several water tanks fore and aft, allowing them to adjust longitudinal trim as well as height.
Some modern designs instead pump lifting gas between the gas bags and storage cylinders. 
Sails are primarily used on the water by sailing ships and sail boats as a propulsion system.
For purposes of commerce, sails have been greatly superseded by other forms of propulsion, such as the internal combustion engine.
For recreation, however, sailing vessels remain popular.
The most familiar type of sailboat, a small pleasure yacht, usually has a sail-plan called a sloop.
This has two sails in a fore-and-aft arrangement: the mainsail and the jib.
The mainsail extends aftward and is secured the whole length of its edges to the mast and to a boom also hung from the mast.
The sails of tall ships are attached to wooden timbers or "spars".
The jib is secured along its leading edge to a forestay (strong wire) strung from the top of the mast to the bowsprit on the bow (nose) of the boat.
A genoa is also used on some boats.
It is a type of jib that is large enough to overlap the mainsail, and cut so that it is fuller than an ordinary jib producing a greater driving force in lighter winds.
A spinnaker is also used on some boats to help move the sailboat faster downwind.
The spinnaker is often a colourful sail and can be either symmetrical or asymmetrical.
Fore-and-aft sails can be switched from one side of the boat to the other in order to provide propulsion as the sailboat changes direction relative to the wind.
When the boat's stern crosses the wind, this is called gybing; when the bow crosses the wind, it is called tacking.
Tacking repeatedly from port to starboard and/or vice versa, called "beating", is done in order to allow the boat to follow a course into the wind.
Modern boats can sail as close as 30 degrees to the wind.
A primary feature of a properly designed sail is an amount of "draft", caused by curvature of the surface of the sail.
When the leading edge of a sail is oriented into the wind, the correct curvature helps maximise lift while minimising turbulence and drag, much like the carefully designed curves of aircraft wings.
Modern sails are manufactured with a combination of broadseaming and non-stretch fabric (ref New technology below).
The former adds draft, while the latter allows the sail to keep a constant shape as the wind pressure increases.
The draft of the sail can be reduced in stronger winds by use of a cunningham and outhaul, and also by bending the mast and increasing the downward pressure of the boom by use of a boom vang.
Other sail powered machines include ice yachts, windmills, kites, signs, hang gliders, electric generators, windsurfers, and land sailing vehicles.
Sail construction is governed by the science of aerodynamics. 
A jibe can be a dangerous maneuver in a fore-and-aft rigged boat because, as the direction of the wind crosses the boat's centerline, the "old" leeward side of the mainsail and boom suddenly becomes the new windward side, and the sails are always fully filled by the wind.
The load on the sail and mainsheet can remain high throughout the maneuver, and if uncontrolled, the boom and mainsail can swing across the deck with high speed, striking and injuring anyone standing in the path of the boom or its tackle, as they sweep across the boat.
An uncontrolled boom slamming to the limit of its range may also put excessive stress on the rigging, and can break the boom or standing rigging, perhaps even bringing the mast down.
A jibe can also result in a sudden change in the direction of heeling, and can cause unexpected course changes due to the change in mainsail force changing from one side of the boat to the other.
Owing to the hazard associated with the accidental jibe, some designers are moving away from designs that require the use of booms.
There are also several designers that have placed the mast in the back of the boat in a configuration termed mast aft.
This enables them to greatly reduce the size of the boom or eliminate it completely.