CLAIMS

1.

An underwater earth moving vehicle comprising: earth moving means; a vehicle body supporting said earth moving means and adapted to actuate said earth moving means by moving in a forward direction ; first thruster means connected to said vehicle body and arranged rearwardly of said earth moving means, said first thruster means having a first position in which said first thruster means in use generates substantially forward thrust, a second position in which said first thruster means in use generates substantially vertical thrust, and at least one third position in which said first thruster means in use generates thrust in a direction between said substantially forward and substantially vertical directions ; second thruster means comprising at least one first thruster and at least one second thruster spaced substantially forwardly of a said first thruster, wherein said second thruster means is adapted to generate substantially sideways thrust ; and third thruster means for generating at least substantially vertical thrust.

2.	A vehicle according to claim 1, wherein said first thruster means is at least partially pivotable between said first and at least one said third position and/or between said second and at least one said third position.

3.	A vehicle according to claim 2, wherein said first thruster means is arranged on at least one support member pivotable relative to said vehicle body, such that said first thruster means is higher in said third position than in said first position.

4.	A vehicle according to any one of the preceding claims, wherein said first thruster means comprises at least one pair of thrusters.

5.	A vehicle according to any one of the preceding claims, wherein at least one said first and/or second thruster is arranged outwardly of said vehicle body in said substantially forward direction.

6.	A vehicle according to claim 5, wherein said second thruster means comprises at least one pair of thrusters comprising a said first thruster and a said second thruster arranged adjacent diagonally opposite corners of said vehicle body.

7.	A vehicle according to any one of the preceding claims. wherein at least one said first thruster is driven independently of at least one said second thruster.

8.	A vehicle according to any one of the preceding claims, wherein said third thruster means is adapted to selectively generate substantially forward thrust or substantially vertical thrust.

9.	A vehicle according to claim 8, wherein said third thruster means is adapted to generate thrust in at least one direction between said substantially forward and substantially vertical directions.

10.	A vehicle according to claim 9, wherein said third thruster means is at least partially pivotable between said substantially forward and said substantially vertical directions.

11.	A vehicle according to any one of the preceding claims, wherein said third thruster means comprises at least one third thruster and at least one fourth thruster spaced sideways of a said third thruster.

12.	A vehicle according to claim 11, wherein at least one third thruster and at least one fourth thruster are arranged adjacent opposite lateral sides of the vehicle body.

13.	A vehicle according to any one of the preceding claims, further comprising electric and/or hydraulic drive means for driving said first and/or second and/or third thruster means.

14.	A vehicle according to claim 13, wherein at least one pair of said thrusters is driven in parallel by a respective single drive means.

15.	A vehicle according to claim 14, wherein the or each said single drive means is hydraulic and comprises at least one valve means for adjusting flow of driving fluid to the individual thrusters of a respective pair of thrusters.

16.

A vehicle according to claim 15, wherein the or each said valve means comprises a respective valve body having a respective pair of fluid passages therethrough, and a respective throttle means for restricting fluid flow in one passage of said pair without restricting flow in the other passage of said pair.

17.	A vehicle according to claim 16, wherein the or each said throttle means comprises a respective throttle member moveable relative to the corresponding pair of passages and having a pair of fluid passage portions, each of which is wider than the corresponding passage.

18.	A vehicle according to any one of the preceding claims, further comprising adjusting means for adjusting the position of the centre of gravity and/or the centre of buoyancy of the vehicle.

19.	A vehicle according to claim 18, wherein said adjusting means comprises weight means movable between a first position and a second position rearwardly of said first position.

20.	A vehicle according to claim 19, wherein said adjusting means comprises buoyancy means movable between a first position and a second position forwardly of said first position.

21.	A vehicle according to any one of the preceding claims, wherein the earth moving means comprises jetting means pivotably attached to the vehicle body.

22.	A vehicle according to claim 21, wherein the jetting means comprises at least one pair of jetting legs adapted to straddle an elongate product to be buried by the vehicle.

23.	A vehicle according to any one of the preceding claims, further comprising control means for controlling said first and/or second and/or third thruster means in response to input signals representing forces acting on the vehicle.

24.	A vehicle according to claim 23, further comprising ground contact means, and wherein said input signals represent forces acting on said ground contact means in a direction substantially perpendicular to said substantially forward direction.

25.	An underwater earth moving vehicle substantially as hereinbefore described with reference to Figures 5 to 13 of the accompanying drawings.