i wouldnt recommend doing it over water because water and any kind of line dont mix well. youll get weird stretching and it will most likely dry with lumps and bumps, and ultimately deteriorates the line faster. but like its posted above, its fairly easy to set it up using a couple carabiners, or you can buy a kit. ive used both a lot and its harder to get the line really tight using carabiners so they arent ideal for freestyle (jumping) slacking. but if you just want to walk and dance around on a 1" line carabiners work just fine.
this is how you thread the line through the carabiners, if you choose to do it that way. (the green things are the carabiners)
hit me with a pm if you have any other questions