ROTATIONAL MOULDED KAYAK WITH INTEGRALLY FORMED UTILITY BIN TECHNICAL FIELD 5 The present invention relates to a rotationally moulded sit-on-top kayak with an integrally formed utility bin. BACKGROUND ART Conventional rotationally moulded sit-on-top kayaks have a seating area, and storage compartments to the front and/or rear of the seating area, for storing general 10 items, and also able to store fish and bait, for when fishing. These compartments are accessed by a hatch covered with a hatch cover which is water tight or semi-water tight. The compartment is simply an open area inside the hull, and consequently, any water getting into the compartment can slosh around inside the hull, and is difficult to bail out. To keep articles in place inside the storage compartments, a bin or bag is often 15 secured inside the compartment, however the size of the bin is limited by the compartment opening, and water etc. can still get into the inside of the hull. Moreover, it is usually difficult to access the storage compartment from the seating area. DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a rotationally moulded sit-on 20 top kayak with an integrally formed utility bin, which addresses the aforementioned shortcomings, or which at least provides the public with a useful choice. According to a first aspect of the present invention there is provided a rotationally moulded sit-on-top kayak including: an integrally moulded hull incorporating a seating section and a leg accommodating section with left and right leg 25 sections for accommodating the legs of an occupant, wherein the moulded hull further includes a utility bin provided between the left and right legs sections, the utility bin being formed integrally with the moulded hull at the time of rotational moulding of the kayak, and with a base section thereof formed apart from an adjacent inside surface of the moulded hull. 30 With such a construction, the utility bin can be easily accessed from the seating section. Moreover, since the utility bin is formed integral with the rotationally moulded hull, any water getting into the utility bin, cannot get into the inside of the hull. Preferably the kayak further includes a lid adapted to cover a top opening of the utility bin. -1- By having a lid, the contents of the utility bin can be kept dry and clean. If the lid has a water tight seal, then the contents can be kept even drier. Preferably, the utility bin is formed with a through opening that communicates between an outside surface of the moulded hull, and an inside surface of the utility bin, 5 and connects between the base section of the utility bin and the adjacent inside surface of the hull, and is provided with a plug for optionally closing the through opening. By having a through opening in the bottom of the utility bin, the bin can be easily drained when the kayak is taken out of the water. Moreover, the bin may be used for a live fish/bait container that is continually filled with clean water from outside of 10 the hull. According to an other aspect of the present invention there is provided a method of manufacturing a sit-on-top kayak with an integrally formed utility bin as described above, including the steps of: making a mould for rotational moulding of the kayak hull including a mould 15 section for the utility bin such that in the completed hull, the base section of the utility bin is formed apart from the adjacent inside surface of the moulded hull; pouring rotational moulding plastic powder into the mould while rotating and heating the mould, to thereby melt the plastic powder so that it flows around the entire internal surface of the mould and forms the hull of the kayak integral with the utility 20 bin; and allowing the mould to cool to solidify the rotational moulding plastic, and then removing the solidified hull from the mould. This invention may also broadly be said to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or 25 collectively, and any or all combinations of any two or more of the parts, elements or features, and where specific integers are mentioned herein which have known equivalents such equivalents are deemed to be incorporated herein as if individually set forth. BRIEF DESCRIPTION OF THE DRAWINGS 30 Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only and with reference to the accompanying drawings in which: FIG. 1 is a plan view of a sit-on-top kayak with an integrally formed utility bin according to the invention; -2- FIG. 2 is an enlarged view of a central part of the kayak of FIG. 1, showing the main parts related to the present invention; and FIG. 3 is an enlarged cross-section view on A-A in FIG. 2. BEST MODES FOR CARRYING OUT THE INVENTION 5 FIGS. I to 3 are schematic diagrams illustrating an embodiment of a rotationally moulded sit-on-top kayak with an integrally formed utility bin according to the invention, generally indicated by arrow 1. As shown in FIGS. 1 to 3, the rotationally moulded sit-on-top kayak 1 includes: an integrally moulded hull 2, incorporating a seating section 4, and a leg accommodating section 6 with left and right leg sections 6a 10 and 6b for accommodating the legs of an occupant. The moulded hull 2 further includes a utility bin 8 provided between the left and right legs sections 6a and 6b. As can be seen more clearly in FIG. 3, the utility bin 8 is formed integrally with the moulded hull 2 at the time of rotational moulding of the kayak 1, with a base section 8a thereof formed apart from an adjacent inside surface 9 15 of the moulded hull 2. With such a construction, the utility bin 8 can be easily accessed from the seating section 4. Moreover, since the bin 8 is formed integral with the rotationally moulded hull 2, any water getting into the bin 8, cannot get into the inside of the hull 2. In this embodiment the sit-on-top kayak 1 further includes a lid 10 adapted to 20 cover a top opening 12 of the utility bin 8. By having the lid 10, the contents of the utility bin 8 can be kept dry and clean. Also since the utility bin 8 is integrally moulded with the hull 2 at the time of manufacture, the dimensions of the top opening 12 of utility bin 8 can be made accurately, so that the lid 10 can be made to fit closely with the opening 12, and give a 25 good seal. If the lid 10 is fitted with a water tight seal member, then the contents of the utility bin 8 can be kept even drier. Moreover in this embodiment, the utility bin 8 is formed with a through opening 14 that communicates between an outside surface 16 of the moulded hull 2, and an inside surface 18 of the utility bin 8, and connects between the base section 8a of the 30 utility bin and the adjacent inside surface 9 of the hull 2, and is provided with a plug 20 for optionally closing the through opening 14. By having the through opening 14 in the bottom of the utility bin 8, the utility bin 8 can be easily drained when the kayak 1 is taken out of the water. Moreover, the -3utility bin 8 may be used for a live fish/bait container that is continually filled with clean water from outside of the hull 2. Manufacture of the sit-on-top kayak with an integrally formed utility bin of the above construction, involves first: making a mould for rotational moulding of the kayak 5 hull 2 including a mould section for the utility bin 8 such that in the completed hull 2, the utility bin 8 base section 8a is formed apart from the adjacent inside surface 9 of the moulded hull 2; pouring rotational moulding plastic powder into the mould while rotating and heating the mould, to thereby melt the plastic powder so that it flows around the entire internal surface of the mould and forms the hull 2 of the kayak 10 integral with the utility bin 8; and allowing the mould to cool to solidify the rotational moulding plastic, and then removing the solidified hull from the mould. INDUSTRIAL APPLICABILITY The invention offers the following advantages in industrial application, however it should be appreciated that all such advantages may not be realised on all 15 embodiments of the invention, and the following list is given by way of example only as being indicative of potential advantages of the present invention. Furthermore it is not intended that the advantages of the present invention be restricted to those of the list which follows: (a) By forming the utility bin integral with the rotationally moulded hull, at a 20 location between the legs of an occupant, the utility bin can be easily accessed from the seating section. Moreover, since the bin is formed integral with the rotationally moulded hull, any water getting into the bin, cannot get into the inside of the hull. (b) By having a lid, the contents of the utility bin can be kept dry and clean. Also since the utility bin is integrally moulded with the hull at the time of manufacture, 25 the dimensions of the bin opening can be made accurately, so that the lid can be made to fit closely with the opening, and give a good seal. (c) By having the through opening in the bottom of the utility bin, the bin can be easily drained when the kayak is taken out of the water. Moreover, the bin may be used for a live fish/bait container that is continually filled with clean water from outside of 30 the hull. Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the invention as defined by the appended claims. -4-