I have a feeling that Elemental Haki might be a thing in the One Piece World. I noticed that certain characters have moves or attacks that include elements but can’t really explain how they use them.
Sanji- his fire kicks dont burn him at all (has yet to go against a logia to show if his kicks would hit or not.)
Zoro- his attack with the swords to create a tornado using wind (he only went against Monet and we saw how that ended)
Luffy- he used a red hawk under water and that dind burn him at all, also what the hell was the snake shot?
Fishmen- could fishmen karate be water haki? (hence why Koala can use it)
Sabo- Sabo use that DragonBreath attack during the Colosseum battle and split the arena with what appear to be wind?
Eustass Kid crewmate- during saboady he used a technic to breath fire
Whitebeard allies-During marine ford there was a guy with electricity on his sword.
Vista- could Vista possibly have earth Haki which would or could be nature like and that would explain the flowers?
Kinemo- this guy cuts fire like its normal.
Brook- his ice abilities seem random to me maybe ice Haki?
Fossa (WB pirate)-was using fire on his sword
Hannyable was able to light the ends of his staff with fire
Those are just some of the samples I could find. If I miss any please comment below and let me know!
*Theory made by Princeton Production. Here is the Original video talking about this theory: