Marine Horseshoe Worm (Phoronopsis californica)
In Wikipedia it mentions only temperate areas but I see links to Indonesia spottings as well;
In this link they even saw it in the same dive site as me. See:
''Phoronopsis californica'' is a species of marine horseshoe worm in the phylum Phoronida. It was first described as a new species by William Hilton in 1930 when he found it at Balboa Bay, California.
Similar species: Not assigned
Uploaded Jul 20, 2018. Captured May 15, 2018 05:50 in Unnamed Road, Kota Bitung, Sulawesi Utara, Indonesia.