I found out that you can actually start up solo lobbies and do acheivements that do not require kills due to you being completely alone.
At main menu click "Create a Game" then choose the map you desire, so for this achievement it is "Bathtub Bash".
Then down the bottom of your screen, Tick the "invite Only" button and press "P2P" this will take you to a lobby and you can just press "Force Start Timer" and away you go :)
Jump off the spawn and into the water 10 times and voila :)