Order: Hydroider (Hydroidea)
| Site | Municipality (county) | Num. obs. | Num. species | Num. images | Last obs. | |
|---|
| Akvastasjonen | Vestland, Norway | 5 | 1 | 0 | 2001-11-26 | |
| Arkavatnet | Rogaland, Norway | 1 | 1 | 0 | 1989-08-28 | |
| Drøbak | Akershus, Norway | 1 | 1 | 1 | 2014-10-15 | |
| Espegrend | Vestland, Norway | 15 | 2 | 0 | 2001-06-11 | |
| Hammervatnet | Trøndelag, Norway | 1 | 1 | 0 | 1989-10-08 | |
| Harestuvannet | Akershus, Norway | 1 | 1 | 0 | 1992-06-12 | |
| Hostadvatnet | Møre og Romsdal, Norway | 1 | 1 | 0 | 1989-09-14 | |
| Husavatnet | Vestland, Norway | 1 | 1 | 0 | 1989-09-28 | |
| Håkonshella | Vestland, Norway | 1 | 1 | 0 | 2013-05-16 | |
| Jarenvannet | Innlandet, Norway | 1 | 1 | 0 | 1991-08-27 | |
| Kolbjørnviksjøen | Østfold, Norway | 1 | 1 | 0 | 1989-09-01 | |
| Kvitblikkvannet | Nordland, Norway | 1 | 1 | 0 | 1989-09-14 | |
| Moensvatnet | Vestland, Norway | 2 | 1 | 0 | 1990-10-25 | |
| Myravatnet | Vestland, Norway | 1 | 1 | 0 | 1989-09-14 | |
| Sagtjernet | Innlandet, Norway | 1 | 1 | 0 | 1989-09-20 | |
| Torvangerfjæra | Vestland, Norway | 1 | 1 | 0 | 2002-10-08 | |
| Træ | Vestland, Norway | 2 | 2 | 0 | 2002-11-07 | |
| Vikerauntjønna | Trøndelag, Norway | 1 | 1 | 0 | 1989-09-27 | |
| Årungen | Akershus, Norway | 1 | 1 | 0 | 1989-09-20 | |