I have no idea what this is
I'm pretty sure this is a type of salp. It was the most unusual thing I have encountered in the ocean. It was between half a meter and a meter in length.
The Thaliacea comprise a class of marine animals within the subphylum Tunicata. Unlike their benthic relatives the ascidians, thaliaceans are free-floating (pelagic) for their entire lifespan. The group includes species with complex life cycles with both solitary and colonial forms.