Just do it right the first time and hook up a GFCI on your power source. trying to overthink and cut corners is a sign to just do it right the first time or else you will do it again. Like someone said.. Might as well hardwire to your pump.. Or get some romex cable and set up a few receptcles near your pond. You never know what kinda things you may want to plug into it.
Just some thoughts and trying to help.
Joe