Summarv of the Invention In a first aspect, the invention provides a submersible floating structure, for mooring watercraft, that can be in the form of a pontoon, marina, or equivalent floating structure. In regions where there are extreme weather conditions, such as icing over of yacht or boat mooring waterways or where cyclonic weather conditions or flooding occur, it is desirable to provide a rapid and easy way of protecting a floating mooring facility without having to move that facility a substantial distance across the water or entirely remove it from the water.

The present invention provides a submersible marina/pontoon or boat mooring facility adapted to be floatingly positioned adjacent a shoreline or moored while unconnected to dry land. The mooring facility is able to rise and fall with tidal changes and secured so as to remain substantially a constant distance from the shoreline during those tidal changes. The floating structure is retained at a predetermined level relative to the water level in a manner similar to that of a diving bell wherein an air vent closed by an air release valve located above the predetermined level is opened to allow the ingress of water through water entry and release ports until the structure settles into the water and the predetermined flotation level is achieved.

Another mode of controlling the flotation of the structure, could be to provide a sealed structure

and pump water into or out of the structure to vary its buoyancy between an operating position and a submerged position. To protect the floating structure from damage such as may occur during cyclonic weather conditions or an icing over of the waterway or excessive tides or flooding, the floating structure can be sunk by opening a buoyancy air release valve so that the structure fills with water and sinks below the surface. If preferred, the depth to which the structure sinks can be controlled by providing a bottom stop which contacts the sea, lake or river bed to hold the structure a predetermined distance above that bed.

A snorkel vent coupled to the air release valve remains above the surface of the water when the structure has been submerged. To refloat the structure, water is ejected from the water entry ports via discharging means, such as conventional spa bath blowing nozzles, which pressurise through the snorkel line. As air is pumped into the interior of the structure through that line, water is discharged through the water entry and release ports and the structure floats upwardly as air replaces water in the interior of the structure.

A second aspect this invention provides a control system for raising and lowering submersible floating structures, e. g. for mooring watercraft, that can be in the form of a pontoon, marina, or equivalent floating structure. Such a structure can be of but is not limited to the form of the first aspect of the invention.

In one example, the second aspect of the present invention provides a control system for controlling the inlet and outlet of a gaseous buoyancy medium to a submersible structure, said structure includes a plurality of buoyancy chambers adapted to be filled with said gas or water and wherein said control system includes gas control valves adapted to be actuated upon application of a predetermined tilt angle to the structure to feed gas into or out of discrete ones of said chambers to maintain a level attitude for said structure during submersion or flotation of said structure.

Brief Description of the Drawings The present invention will now be described by way of example with reference to the accompanying drawings, in which:- Fig 1 is a diagrammatic plan view of an embodiment of the first aspect of the present invention; Fig 2 is diagrammatic front elevation view of the embodiment of Fig 1 in the direction 11-11; and Fig. 3 is a schematic of one embodiment of a control system in accord with the second aspect of the present invention when fitted to a submersible pontoon.

Detailed Description of Preferred Embodiments In Figs 1 and 2, a submersible pontoon structure 10 is connected to the shoreline 11 via a gangway 12 and shore anchor 13. Positioning of the pontoon floating structure 14 is controlled by a hinge mounting 15 with pile 16 at one end and mooring blocks/anchors 17 tethered to the pontoon 10 at its opposite end.

Floating structure 14, incorporates an air release and entry valve 18 controlling flow through snorkel tube 19. Water entry and release holes 20 allow water to enter into structure 14 upon opening of valve 18 until the desired freeboard of structure 14 is obtained or the structure is submerged, as appropriate.

A bottom stop 21 depending below structure 14 provides a restraint preventing structure 14 from settling onto the seabed 22 when the structure is submerged. In this embodiment, pile 16 includes a bottom stop 23 which abuts the underside of slidable hinge mounting 15.

An upper stop 24 is included on pile 16 and it may function as a trigger, when contacted by hinge 15, to activate opening of valve 18 to allow structure 14 to sink as could occur during storm or flood conditions.

In Fig. 3, a plan view of a pontoon 10 is formed with four buoyancy chambers or flotation modules 30, one located in each corner of pontoon 10.

Each buoyancy chamber 30 has an air entry and release port or hole 31 in its uppermost extremity with an air or gas line 32 for ingress and exit air. In each line 32 there is a valve 33 which opens or closes line 32.

Each air line 32 is connected to a pontoon level control valve 34, with air lines 32 of diagonally opposed modules 30 being interconnected via pairs of non-return valves 35 to an opposite side of a respective ball valve 36 to ensure the appropriate direction of flow of air into or out of buoyancy chambers 30 during raising or lowering of pontoon 10 when floating on water.

If pontoon 10 tilts during raising, with air going into each chamber 30, it is necessary for the control valve 34 which is feeding air into the upwardly tilted chamber 30 to stop feeding that chamber while the diagonally opposed downwardly tilting chamber 30 requires additional air to be fed to it. In the case of tilting of pontoon 10 during lowering the reverse is required where more air is required to be removed from the upwardly tilted chamber 30 than its diagonally opposed downwardly tilted chamber 30.

Redirecting of air flow in lines 32 as a result of tilting during lowering or raising of pontoon 10 is effected by having all of valves 36, which are formed as ball valves in the embodiment, either open or closed, respectively.

During air addition with ball valves 36 closed air is directed through one tilt sensitive valve 34 and a respective chamber 30 while during air removal with ball valves 36 opened,

air is directed through the diagonally opposite valve 34. This alternating of diagonally opposed tilt valves 34 depending upon whether or not pontoon 10 is being raised or lowered takes into account the actuation of the tilt valves on the basis that each tilt valve 34 is able to be actuated in only one tilt direction. The tilt valves 34 in this embodiment are pendulum operated valves.

With pontoon 10 on a sea, lake or river bed with buoyancy air release and entry valves 33 open, the valves 36 can be closed and pressurised air then fed into line 37 to pass into each chamber 30 through a valve 34. Inlet air passes through a valve 34 then a non- return valve 35 and through a line 32 and valve 35 to chamber 30.

If during raising of the pontoon 10 a tilt occurs such that one valve 34 is closed, that valve 34 needs to be the one that feeds air to the upwardly tilted chamber 30 while air continues to be fed to the diagonally opposite chamber 30. Once the tilt is reduced to a predetermined position, preferably when the pontoon is again level, the closed valve 34 re- opens to continue feeding pressurised air to raise the pontoon in its level attitude.

When pontoon 10 has been raised to a desired level of flotation, valves 33 are closed to maintain that level and the air supply to line 37 can be disconnected.

Lowering of pontoon 10 to achieve a level attitude while sinking is conducted by carrying out the reverse procedure. In this case air flows from a chamber 30 through valve 33 in a line 32 then through an open valve 36, a pendulum operated valve 34 and out to atmosphere through line 37.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.