i would get the motor,esc,coupler,cooling jacket,mount. that way you can spend a bit of time putting it together and work out what goes were.
the esc cooling plate is not needed as the etti already has one, and get this cooling jacket its the xl size http://www.offshoreelectrics.com/pro...ose-mjacket-XL
thats every thing from o.s.e you mite need so only one lot of shipping costs.
when your ready to get batteries from hobby king it will pay to get some 5.5mm plugs and probably a ubec, o.s.e does sell a ubec as well, if you was running the boat with a nitro chances are you will have a battery pack for the receiver any way