Hi "s"!
> Fleshy invertebrates ranging in size from about 1cm to 4 or 5cm attached to
> a plastic film (ocean debris).When squeezed or stepped on, the organism ejects
> filaments of *bright* neon orange (tentacles?) from what appears to be it's
> mouth.
Sounds like an actinia or anemone. They belong to the same Phylum as the
"Jellyfish" do - Cnidaria. "Ask" Google ( www.google.com ) for some pictures
(try anemone, actinia and cnidaria together or anthozoa and actinia together)
and look if that's what you've seen!
greetings, Martina