| Family | Common Name | Selected Genus and Species | Image |
|---|---|---|---|
| Halammohydridae | Hydrozoan | Halammohydra schulzei | |
| Otohydridae | Hydrozoan | Otohydra vagans | |
| Family | Common Name | Selected Genus and Species | Image |
|---|---|---|---|
| Acaulidae | Hydroid | Acaulis ilonae |  |
| Asyncorynidae | Hydroid | Asyncoryne ryniensis |  |
| Australomedusidae | Hydroid | Australomedusa thrombolites |  |
| Balellidae | Hydroid | Balella mirabilis |  |
| Boeromedusidae | Hydroid | Boeromedusa auricogonia |  |
| Boreohydridae | Hydroid | Plotocnide borealis |  |
| Bougainvilliidae | Hydroid | Bougainvillia muscus |  |
| Bythotiaridae | Hydroid | Eumedusa birulai |  |
| Candelabridae | Gnome's Hat Hydroid | Candelabrum capensis |  |
| Cladocorynidae | Hydroid | Cladocoryne floccosa |  |
| Cladonematidae | Hydroid | Cladonema pacificum |  |
| Clathrozoellidae | Hydroid | Clathrozoella bathyalis |  |
| Cordylophoridae | Hydroid | Cordylophora caspia |  |
| Corymorphidae | Nodding Sea Fir | Corymorpha nutans |  |
| Corynidae | Hydroid | Stauridiosarsia cliffordi |  |
| Cytaeididae | Hydroid | Perarella schneideri |  |
| Eucodoniidae | Hydroid | Eucodonium brownei |  |
| Eudendriidae | Hydroid | Eudendrium ramosum |  |
| Halimedusidae | Hydroid | Halimedusa typus |  |
| Heterotentaculidae | Hydroid | Heterotentacula mirabilis |  |
| Hydractiniidae | High-spined Commensal Hydroid | Hydractinia altispina |  |
| Hydrichthyidae | Hydroid | Hydrichthys sarcotretis |  |
| Hydridae | Hydroid | Hydra viridissima |  |
| Hydrocorynidae | Hydroid | Hydrocoryne miurensis |  |
| Jeanbouilloniidae | Hydroid | Jeanbouillonia maserati |  |
| Magapiidae | Hydroid | Magapia jaumotti |  |
| Margelopsidae | Hydroid | Margelopsis haeckeli |  |
| Milleporidae | Hydroid | Millepora dichotoma |  |
| Moerisiidae | Hydroid | Odessia maeotica |  |
| Niobiidae | Hydroid | Niobia dendrotentaculata |  |
| Oceaniidae | Hydroid | Oceania armata |  |
| Pandeidae | Hydroid | Leuckartiara ruberiverruca |  |
| Paracorynidae | Hydroid | Paracoryne huvei |  |
| Pennariidae | Christmas Tree Hydroid | Pennaria disticha |  |
| Porpitidae | Blue Button | Porpita porpita |  |
| Proboscidactylidae | Hydroid | Proboscidactyla flavicirrata |  |
| Protiaridae | Hydroid | Protiara haeckeli |  |
| Protohydridae | Hydroid | Sympagohydra tuuli |  |
| Ptilocodiidae | Hydroid | Hydrichthella epigorgia |  |
| Rathkeidae | Hydroid | Rathkea octopunctata |  |
| Rhysiidae | Hydroid | Rhysia fletcheri |  |
| Rosalindidae | Hydroid | Rosalinda incrustans |  |
| Similiclavidae | Hydroid | Similiclava nivea |  |
| Solanderiidae | Grey Fan Hydroid | Solanderia procumbens |  |
| Sphaerocorynidae | Hydroid | Astrocoryne cabela |  |
| Stylasteridae | Hydroid | Stylaster nobilis |  |
| Teissieridae | Hydroid | Teissiera polypofera |  |
| Trichydridae | Hydroid | Trichydra pudica |  |
| Tricyclusidae | Hydroid | Tricyclusa singularis |  |
| Tubiclavoididae | Hydroid | Tubiclavoides striatum |  |
| Tubulariidae | Tubular Hydroid | Ectopleura crocea |  |
| Zancleidae | Hydroid | Zanclea alba |  |
| Zancleopsidae | Hydroid | Zancleopsis dichotom |  |
| Family | Common Name | Selected Genus and Species | Image |
|---|---|---|---|
| Aglaopheniidae | Hydroid | Aglaophenia cupressina |  |
| Aequoreidae | Crystal Jellyfish | Aequorea victoria |  |
| Barcinidae | Jellyfish | Barcino foixensis |  |
| Blackfordiidae | Black Sea JellyfishBlack Coral | Blackfordia virginica |  |
| Bonneviellidae | Hydroid | Bonneviella superba |  |
| Campanulariidae | Hydroid | Obelia geniculata |  |
| Campanulinidae | Hydroid | Calycella syringa |  |
| Cirrholoveniidae | Jellyfish | Cirrholovenia tetranema |  |
| Clathrozoidae | Hydroid | Clathrozoon wilsoni |  |
| Dipleurosomatidae | Jellyfish | Dichotomia cannoides |  |
| Eirenidae | Jellyfish | Tima formosa |  |
| Haleciidae | Sea Hedgehog Hydroid | Halecium muricatum |  |
| Halopterididae | Fine Hydroid | Corhiza scotiae |  |
| Hebellidae | Jellyfish | Hebella scandens |  |
| Kirchenpaueriidae | Hydroid | Kirchenpaueria pinnata |  |
| Lafoeidae | Hydroid | Lafoea dumosa |  |
| Laodiceidae | Jellyfish | Ptychogena crocea |  |
| Lineolariidae | Hydroid | Lineolaria spinulosa |  |
| Lovenellidae | Hydroid | Lovenella assimilis |  |
| Malagazziidae | Jellyfish | Malagazzia hirsutissima |  |
| Melicertidae | Jellyfish | Melicertum octocostatum |  |
| Mitrocomidae | Jellyfish | Mitrocomella polydiademata |  |
| Octocannoididae | Jellyfish | Octocannoides ocellata |  |
| Orchistomatidae | Jellyfish | Orchistoma agariciforme |  |
| Phialellidae | Jellyfish | Phialella zappai |  |
| Phialuciidae | Jellyfish | Phialucium mbengha |  |
| Phylactothecidae | Hydroid | Hydrodendron gorgonoide |  |
| Plumaleciidae | Hydroid | Plumalecium plumularioides |  |
| Plumulariidae | Plumed Hydroid | Plumularia setacea |  |
| Schizotrichidae | Hydroid | Schizotricha frutescens |  |
| Sertularellidae | Hydroid | Sertularella polyzonias |  |
| Sertulariidae | Jointed Hydroid | Thuiaria articulata |  |
| Staurothecidae | Hydroid | Staurotheca vanhoeffeni |  |
| Sugiuridae | Hydroid | Sugiura chengshanense |  |
| Symplectoscyphidae | Hydroid | Symplectoscyphus tricuspidatus |  |
| Syntheciidae | Hydroid | Synthecium protectum |  |
| Teclaiidae | Hydroid | Parateclaia norvegica |  |
| Tiarannidae | Hydroid | Stegopoma plicatile |  |
| Tiaropsidae | Hydroid | Tiaropsidium kelseyi |  |
| Zygophylacidae | Hydroid | Zygophylax kakaiba |  |
| Family | Common Name | Selected Genus and Species | Image |
|---|---|---|---|
| Armorhydridae | Hydroid | Armorhydra janowiczi |  |
| Microhydrulidae | Hydroid | Microhydrula pontica |  |
| Monobrachiidae | Hydroid | Monobrachium parasitum |  |
| Olindiidae | Flower-hat Jellyfish | Olindias formosus |  |
| Family | Common Name | Selected Genus and Species | Image |
|---|---|---|---|
| Aeginidae | Jellyfish | Bathykorus bouilloni |  |
| Csiromedusidae | Jellyfish | Csiromedusa medeopolis |  |
| Cuninidae | Dinner-plate Jellyfish | Solmissus marshalli |  |
| Pseudaeginidae | Jellyfish | Pseudaegina pentanema |  |
| Solmarisidae | Jellyfish | Pegantha clara |  |
| Solmundaeginidae | Jellyfish | Solmundella bitentaculata |  |
| Tetraplatiidae | Jellyfish | Tetraplatia volitans |  |
| Family | Common Name | Selected Genus and Species | Image |
|---|---|---|---|
| Abylidae | Hydrozoan | Abylopsis tetragona |  |
| Agalmatidae | Hydrozoan | Marrus orthocanna |  |
| Apolemiidae | Hydrozoan | Apolemia uvaria |  |
| Clausophyidae | Hydrozoan | Chuniphyes multidentata |  |
| Cordagalmatidae | Hydrozoan | Cardianecta parchelion |  |
| Diphyidae | Hydrozoan | Dimophyes arctica |  |
| Erennidae | Hydrozoan | Erenna laciniata |  |
| Forskaliidae | Tubular Siphonophore | Forskalia edwardsii |  |
| Hippopodiidae | Hydrozoan | Hippopodius hippopus |  |
| Physaliidae | Portuguese Man o' War | Physalia physalis |  |
| Physophoridae | Hydrozoan | Physophora hydrostatica |  |
| Prayidae | Hydrozoan | Praya dubia |  |
| Pyrostephidae | Hydrozoan | Pyrostephos vanhoeffeni |  |
| Resomiidae | Hydrozoan | Resomia persica |  |
| Rhizophysidae | Flying Spaghetti Monster | Bathyphysa conifera |  |
| Rhodaliidae | Hydrozoan | Dromalia alexandri |  |
| Sphaeronectidae | Hydrozoan | Sphaeronectes irregularis |  |
| Stephanomiidae | Hydrozoan | Stephanomia amphytridis |  |
| Tottonophyidae | Hydrozoan | Tottonophyes enigmatica |  |
| Family | Common Name | Selected Genus and Species | Image |
|---|---|---|---|
| Geryoniidae | Jellyfish | Liriope tetraphylla |  |
| Halicreatidae | Jellyfish | Botrynema ellinorae |  |
| Petasidae | Jellyfish | Petasus atavus |  |
| Ptychogastriidae | Jellyfish | Ptychogastria polaris |  |
| Rhopalonematidae | Deep Red Jellyfish | Crossota norvegica |  |