>>23555957>>23555986>Amanitas are red and white.And Paras' are red and yellow. They look certainly way more like amanitas than the white-brown common mushrooms, that you suggested. As well as nothing in Tentacruel's description remotely hints at any man o' war inspiration, like half the body being above water and moving with the help of wind on its sail and not even being completely underwater at any given time.
I guess I could see the black part somewhat, but the top still looks 10x more like a jellyfish cap than a fucking sail of a Portuguese man o' war.
Also you should mention that Tentacool has some inspiration from squids(with the two long tentacles) and tentacruel with octopuses( with the form of the tentacles, as well as the beak.
Also, you should really drop the "is based on" formulation, since we're all just posting our theories here.