Board Thread:General discussion/@comment-92.14.209.239-20121223152332/@comment-3974211-20130302203855

Bilgewater and Gunblade do not stack - they share a cooldown.

Blade of the Ruined King does not share a cooldown with the above, though. So you can use Bilgewater + BotRK, or Gunblade + BotRK if you so wish.