Underwater structures

1. An underwater structure comprising:

a support structure;

a power generating apparatus; and

a coupling for coupling the power generating apparatus with the support structure, the coupling having a first configuration in which the power generating apparatus is removable from the support structure, and a second configuration in which the power generating apparatus is not removable from the support structure, wherein, in the second configuration, the coupling is arranged to allow the power generating apparatus to rotate with respect to the support structure about a substantially vertical axis thereof, and to transfer all other mechanical loads from the power generating apparatus to the support structure.

2. A structure as claimed in claim 1 , wherein the coupling comprises:

an attachment portion for attaching the coupling to the power generating apparatus;

an engagement portion adapted for slidable engagement with a locating portion of the support structure; and

a clamp mechanism movable between a release position in which the power generating apparatus and the support structure are releasable from one another, and an engaged position in which the power generating apparatus and the support structure are not substantially releasable from one another.

3. A structure as claimed in claim 2 , wherein the clamp mechanism comprises a first clamp portion, a second clamp portion rotatably attached to the first clamp portion, and an actuator operable to move the first and second clamp portions relative to one another between a release position and an engaged position.

4. A structure as claimed in claim 2 , wherein the clamp mechanism comprises a first clamp portion, and a second clamp portion, wherein the first and second clamp portions are connected to one another by a pair of actuators which are operable to move the first and second clamp portions relative to one another between a release position and an engaged position.

5. A structure as claimed in claim 2 , wherein the clamp mechanism comprises a band clamp to engage movable elements of the coupling with at least one mating feature of the power generating apparatus and support structure.

6. A structure as in claim 1 , wherein the coupling can be engaged with and disengaged from the support structure irrespective of an orientation of the power generating apparatus about the substantially vertical axis.

7. A structure as in claim 1 , further comprising a friction brake which is operable to prevent rotation of the power generating apparatus with respect to the support structure.

8. A structure as claimed in claim 7 , wherein the friction brake is provided by the coupling.

9. A structure as in claim 1 , further comprising a mechanical key operable to lock the rotational position of the power generating apparatus with respect to the support structure.

10. A structure as in claim 9 , wherein the mechanical key is provided by the coupling.

11. A structure as in claim 1 , wherein the power generating apparatus and support structure have respective mating features, which engage with one another, thereby transferring substantially horizontally acting loads directly between the power generating apparatus and the support structure, such that the coupling does not transfer such horizontal loads.

12. A structure as in claim 1 , further comprising alignment guides adapted to align the power generating apparatus with the support structure.

13. A structure as in claim 1 , wherein the coupling is operable to move radially outwardly or radially inwardly of the power generating apparatus in a substantially horizontal plane to engage with one or more features on the support structure.

14. A structure as in claim 1 , further comprising a position stop to prevent the power generating apparatus rotating beyond a predetermined angle.

15. A structure as in claim 1 , further comprising a pin or latch or equivalent mechanical lock adapted to prevent the coupling becoming inadvertently disengaged once it has been engaged, thereby preventing accidental release of the power generating apparatus from the support structure.

16. A coupling for coupling a power generating apparatus with a support structure, the coupling having, in use, a first configuration in which the power generating apparatus is removable from the support structure, and a second configuration in which the power generating apparatus is not removable from the support structure, wherein, in the second configuration, the coupling is arranged to allow the power generating apparatus to rotate with respect to the support structure about a substantially vertical axis thereof, and to transfer all other mechanical loads from the power generating apparatus to the support structure.

17. A coupling as claim 16 , comprising:

an attachment portion for attaching the coupling to a power generating apparatus;

an engagement portion adapted for slidable engagement with a locating portion of a support structure; and

a clamp mechanism movable between a release position in which, in use, the power generating apparatus and the support structure are releasable from one another, and an engaged position in which, in use, the power generating apparatus and the support structure are not substantially releasable from one another.

18. A coupling as claimed in claim 17 , wherein the clamp mechanism comprises a first clamp portion, a second clamp portion rotatably attached to the first clamp portion, and an actuator operable to move the first and second clamp portions relative to one another between a release position and an engaged position.

19. A coupling as claimed in claim 17 , wherein the clamp mechanism comprises a first clamp portion, and a second clamp portion, wherein the first and second clamp portions are connected to one another by a pair of actuators which are operable to move the first and second clamp portions relative to one another between a release position and an engaged position.

20. A coupling as claimed in claim 17 , wherein the clamp mechanism comprises a band clamp to engage movable elements of the coupling with at least one mating feature of a power generation apparatus and support structure.

21. A coupling as claimed in claim 17 , further comprising a friction brake which, in use, is operable to prevent rotation of the power generating apparatus with respect to the support structure.

22. A coupling as in claim 17 , further comprising a mechanical key which, in use is operable to lock the rotational position of the power generating apparatus with respect to the support structure.