—-> Sims VIP created a guide on how to transfer or move diving lots from Isla Paradiso into other worlds of your own.
This also enables you to edit them in the Edit Town mode.
-In short, you need to use | testingcheatsenabled true | buydebug on | enablelotlocking true | in your cheatbox (CTRL + SHIFT + C) to be able to edit the lots. You then save them into your lot bin with all your other saved community and residential lots, open another world, place an empty lot via the edit town tool (in the water of course), lock it (the lock in the corner of your lot description – use testingcheatsenabled true for that). Make sure you choose the Diving Lot as your lot type, save and enter menu. Load your game. All lots should be fine. You can now use the dive spot you just saved on the empty “dive spot” commercial lot.
—–> Guide to Houseboats in game & in CAW (Official TS3 forum post) by SimGuruSemedi gives you:
-FAQ – All questions regarding Houseboats answered.
-Edit Town Tutorial – How to add a houseboat to a world using the in-game editing tools.
-CAW Tutorial – How to build a custom world with the Create a World tool that has houseboats.
…and everything else on houseboats.
*Houseboats cannot be used in combination with the following types of lots: Beach ,Horse Ranch ,Equestrian Center ,Diving Lot ,Port
*You cannot add houseboats on the lake in Twinbrook because it’s considered a lake above sea level >.<
*Houseboats CAN be placed on normal lots, but the houseboat hull will be removed.
*from Edit Town Bin you can place any houseboat on any empty port but the size and shape of the houseboat hull must match.
*To be able to fish off the side of a houseboat, a Sim needs a minimum of three tiles wide and two tiles deep of free space along the edge of a houseboat. Must not be obstructed.