More details for those interested in the siphoning algae:
PHYLOGENETIC ANALYSES OF THE BRYOPSIDALES (ULVOPHYCEAE,
CHLOROPHYTA) BASED ON RUBISCO LARGE SUBUNIT GENE SEQUENCES1
www.ohio.edu/people/lam/Documents/Lam_Zechman.pdf
From it in part:
"The order Bryopsidales (also referred to as the
Caulerpales, Codiales, and Siphonales) is comprised
of green, mostly macroscopic, siphonous algae with
multicellularity arising only in some taxa during sexual
reproduction (Silva 1982). The Bryopsidales exhibit a
cosmopolitan distribution; however, some groups are
restricted to tropical marine environments. One genus,
Dichotomosiphon, is found in freshwater habitats.
Similarly, the Bryopsidales exhibit extremely broad
morphological diversity (from the simple uniaxial siphonous
construction found in Bryopsis, Derbesia, and
Caulerpa to the complex interwoven multiaxial siphon
patterns found in Codium, Halimeda, and Penicillus).
Some genera are heavily calcified as in the genus Udotea,
while the family Caulerpaceae and the majority of
the suborder Bryopsidineae exhibit no calcification.
Some bryopsidalean taxa are invasive and ecologically
problematic and are known to flourish in temperate
marine waters (e.g. Caulerpa taxifolia and Codium fragile
subsp. tomentosoides; Bouk and Morgan 1957, Trowbridge
1995, Jousson et al. 1998)."