Yes, they are right next to each other.
Maybe have a Google for the pictures of the boat dock in Citywalk.....each hotel has it`s own little spot. You can get on any boat from there.
Yes, you go through security before you get on any boat, once you are in Citywalk you`re fine. And again, you`ll get checked before you get on the boat leaving the other hotel too.
But the Citywalk security checks from the hotels if you are walking aren`t normally bad, there`s very rarely a line. Very different from the main Citywalk entrance from the parking lot.