Diggs - DO NOT get the blue waterbed adapter. They are trash and should be thrown away. The threads on the LaunchPad sacs are not strong enough, the fittings will leak constantly and if you ever try and move the sac around or ANYTHING, it can come off completey, letting out LOTS of water.
If you really want, use the barbs Spencer is talking about and GLUE them into the sac. Then hose clamp the hose onto the fitting (so it's removable).
Personally though, I got REALLY sick of the Launch Pads so I moved up to FlyHigh and have had zero worries or incidents.