27 — Not the hydroids you are looking for, thecate hydroids

Thecate hydroid colony, under Ngapipi Bridge,
Tamaki Drive 19/9/16.

Thecate hydroid colony, under Ngapipi Bridge,
Tamaki Drive 19/9/16.

Thecate hydroid colony, under Ngapipi Bridge,
Tamaki Drive 19/9/16. Looking inside the colony
from above.

These are thecate hydroids. Like the athecate hydroids they like places where there's something to attach to, but also lots of current. These colonies come from underneath Ngapipi Bridge, along Auckland's Tamaki Drive, where there is a large tidal flow.



































More info:

A NIWA monograph on New Zealand thecate hydroids

http://www.teara.govt.nz/en/biographies/5r4/ralph-patricia-marjorie