Absent the intent for folks to enter the water, there's no requirement that there be any receptacle ... or, if you prefer, you can have one right at the waterline.
Though ... you know, I COULD put one of those to use in my yard, sort of a 'poor mans hot tub.' To be honest, the things probably cost as much as a real Jacuzzi - heavy plastic isn't cheap - and, by the time I got done, I'd have a $20K DIY tub. Some savings.
Just got my Cabela's catalog and .... yup, they have INFLATABLE, portable hot tubs, just plug into any receptacle.
