I haven't a clue myself, I only can go from my own experience.
All I can draw from is who I've noted are ISFPs. Often they are artist. The high that bob Marley often has gives off a very chill, easy-going vibe. His behavior, his gesture, even his eyes, note for something FP - most definately, but what are those other two letters?
The trouble I'm having is what is the difference between an S and an N visually? What can be withdrawn from his interactions. Even in his history there must be some action that says "Oh, only an S would do that..." or an "S would think that."
However, I think we are all very familiar with his writings/lyrics/songs and ultimately there is something very E about that. And I'd reckon there isn't anything to be said about him being an ESFP - that is just too far fetch. When I think ESFP, I think Magic Johnson - and no matter how cool Magic gets, he'll never strike that cord with me that Bob Marley does.
So, I reckon he has gotta be a ENFP...right?
Well, here is the trouble. ISFPs are often listed with such great names as Bob Dylan, Jimi Hendrix, and my favorite Andre 3000. These are guys that unbeknowest to me, shy from the spotlight when the stage isn't there. Bob Marley never came across as someone affected by the spotlight, and seemed to be putting on a masquerade (not a fascade) or an exaggeration of himself when he hit the stage. There was little flamboyant about him, i.e Jimi Hendrix's way of dressing, or Andre 3000's extravegent sets.
So I'm leaning ENFP, but I can definately see how he could come across as ISFP - especially in his interviews. Really, I just want someone to prove me wrong so I can say "There we go...We lost another one."