These are all fake. Everything has been glued onto assorted 'pet trade' terrapin species, which are almost exclusively freshwater species. This is animal cruelty / mishandling for revenue (especially chucking them in nets to 'release them'), under the guise of 'rescue'.

Though marine turtles sometimes do accumulate agglomerations like those in the videos, if in that state they're either seriously ill (and in urgent care of veterinary intervention) or held in poor captive conditions where they have limited movement (access to rocks/reefs upon which to clean themselves). But none of these are marine turtles. Further, there are very few brackish species - notably the diamondback terrapin (Malaclemys terrapin) - and, as far as I can tell, aren't presented in these videos either.

So yup, looks like some folks have just been collecting / buying sliders and attaching a whole loads' guff onto their backs, and chucking them into the sea, for clicks. Sad.