Rendering floating abjects.
I've created an ocean, which is animating in playback and redering fine, however when i ad an object (cube) and make it float "make motor boats", it will animate fine in the playback but when i render out a short clip (approx 50 frames) the ocean animates but the object itself doesn't. The ocean still intersects around the object, spills over the edge etc, but the object doesn't move at all.
I've also noticed that when i close my scene and then reopen it i loose the animation of the floating object in the maya playback.
Any thoughts???