This invention relates to a device used for observing underwater objects whilst floating on the surface of the water.

It is known to observe sub-marine life by viewing through a glass-bottomed boat. Such a boat is comparatively expensive and not readily portable.

It is also known to observe similar life through goggles whilst the observer lowers his head beneath the surface of the water, using a "snorkel" type of breathing apparatus. Some observers of marine life find this latter method objectionable and often nauseating, preferring to retain their head above the water level.

It is also known for under-water observation and investigation to provide a submarine vessel whereby observation may be kept from within the vessel and through part-spherical windows. In British patent 2194490 there is disclosed a submarine vessel having a first part-spherical window and a second window which may be convex or planar on the concave side of the first window, and the intervening space is filled with a fixed quantity of fluid trapped therein. Such a window is complicated and expensive to produce and the vessel incorporating the window is not readily portable.

British patent 1397456 shows a ^' float board having a pair of spaced apart planar water-tight windows and an observer may float on the surface of the water, supported by the surf board whilst observing under¬ water objects.

British patent specification 2165186-A discloses a buoyant support with a pair of transparent windows having an air gap therebetween.

British patent specification 2188881-A shows a float board having a single lens set into a well,

formed in the board.

European patent 0396829 shows a motor-driven viewing platform having a lens through which a user observes under-water objects. US patent 3808621 shows a balloon-shaped float having a generally spherical depression in its upper surface, the bottom surface being transparent and curved to provide a lensing action.

In British patent 2194490 and European patent 0396829 the devices are complicated and expensive to make and difficult to transport.

In each of British patent specifications 1397456 and 2165186 and US 3808621 a pair of transparent windows are provided having an air gap therebetween. In British patent specification 2188881 a single window is provided which does not provide any magnification of the under-water objects.

It is an object of this invention to provide a device which enables an observer to clearly view marine objects while floating on the surface of the water and providing useful magnification of viewed objects, the device being lightweight and readily portable, and/or improvements generally.

According to the present invention there is provided a device for use in observing sub-marine objects as claimed in the accompanying claims.

Thus, one aspect of the present invention provides a device for use in observing sub-marine objects. The device is provided with means for floating it in the water. For example, the device may be incorporated into a float for use by a swimmer. A further possibility would be for the device to be incorporated into some other floating object such as the bottom portion of a boat. In accordance with the teaching of the invention, there is provided a viewing window. The viewing window comprises generally planar

sheets of a transparent medium such as glass, perspex or the like. These sheets are spaced apart and between them there is provided water or an alternative liquid. it is found that by this arrangement, the user viewing sub-marine objects from above the device, ie from a viewing position in the atmosphere, there is achieved a magnification effect despite the fact that the window does not incorporate any significant curvature in the manner of a lens. Accordingly, an embodiment in accordance with this aspect of the invention provides a magnification effect in an extremely simple manner and at a low cost.

In accordance with a second aspect of the invention, there is provided an embodiment in which a device for use in observing sub-marine objects comprises spaced apart windows provided with means for introducing water into the space between the windows, thereby to achieve the above-discussed magnifying effect. This embodiment is characterised by the feature that the space between the windows is in the form of a chamber, defined in part by the transparent material of the spaced apart window elements, and there is included port means permitting filling and emptying of the chamber with water from the sea, river, swimming pool or other body of water in which the device is to be used. Thus, this embodiment of this second aspect of the invention enables the above- identified magnifying effect to be achieved in a convenient manner by means of an in-situ filling of the chamber with water at the time of use. After use, the port means permits the chamber to be emptied whereby the device is significantly lightened in weight so that the device is more readily carried. This latter advantage is of significance in relation to the use of the device in a float body for use in

swimming. In this embodiment, the spaced transparent sheets of the window will preferably be planar, but not necessarily so. Preferably, at least two ports will be provided giving access to the chamber from the body of water in which the device is to be floated, thereby permitting simultaneous entry of water and exit of air, and vice-versa.

In a described embodiment, the ports providing access to the chamber for the passage of air and water are provided by forming profiled, for example tapered edges at two locations on the inner periphery of a float device having the window located generally centrally therein. The ports thus provide access to the chamber below the edge of the upper sheet of glass defining the chamber. The ports are, in effect, moulded in the material of the float.

In an embodiment of the invention there is provided a device for use in observing sub-marine objects comprising a float member capable of supporting the weight of a user, and being provided with at least two spaced apart windows, having passageways connecting the exterior of the device with the space between the windows.

The above and other features of the invention will become clear from the following description which is given by way of example only with reference to the accompanying drawings in which :

Fig 1 is a plan view of a float device according to the invention; Fig 2 is a section on the line II-II of Fig 1; and

Fig 3 is a section view on the line III-III of Fig 1 to a larger scale.

As seen in the drawings, a float 2 according to the invention comprises a main body 4 having an outer skin 6 formed in two parts, an upper half 8 and a

lower half 10 each formed by a vacuum forming technique and welded together at a median joint line to provide a hollow body which is filled with expanded polystyrene 12 or other suitable material which has a specific gravity lower than 1.

The central part of the body is formed with a rectangular hole 14, the periphery of which is provided with recesses 16 (see particularly the enlarged portion of Fig 2) . Rubber gaskets 18 are fixed within the recesses 16 and plates 20 of clear plastics material, such as acrylics are sealed within the gaskets to form a double-skinned window.

The upper portion 8 has formed therein passageways 17 leading into the hole 14. In use, the device is first immersed beneath the surface of eg the sea to enable water to pass through the passageways 17 into the space between the plates 20. The user then supports his weight on the float whilst observing the marine life or other sub-marine objects through the lens provided by the double- skinned window and the water sandwiched therebetween. The magnification effect of the water between the two skins of the window gives an added interest to the viewer. When the user leaves the sea or other water, he simply inverts the float to empty the water and from the space between the plates 20 by way of the passageways 17.

Although the specific embodiment described and illustrated makes reference to an outer skin filled with expanded polystyrene or other suitable material, the float may, without departing from the invention, comprise an inflatable envelope or casing of similar configuration. In that case, a suitable valve is incorporated for use in inflating or deflating the casing.