These are the tentacles of a peanut worm (Themiste sp.)! The body of the peanut worm is buried below the sediment. The tentacles are extended for feeding, but they can also be withdrawn when needed (e.g., for protection).
To watch a sequence of a peanut worm pulling in its tentacles, review the post from 20 July 2014.
And in case you were wondering — a sea cucumber's tentacles can look very similar. But note that the peanut worm's tentacles lack the shiny ossicles of a sea cucumber. This is especially apparent in the main tentacle branches. To compare, check the photos in the sea cucumber post from 16 April 2013.