ausmick said..
.... They say no skateboards or surfboards? ....
I can understand no skateboards so no knob head rides around the decks making an arse of himself (although I would love to see some joker grind the rail of a ship ... and fall in ...)
As for kite gear, it's none of their business what you put in your bag. I would have through cruise ships would have no real limits on baggage provide it fits in your cabin.
However, as has been said, why spoil a cruise ship holiday lugging kiteboarding gear along? Do you know if the ship is going to stop anywhere you're going to be able to use it, and have time to use it?