| Order | Family | Species | Occurrence | SeaLifeBase name | Name |
|---|---|---|---|---|---|
| Suberitida | Suberitidae | Aaptos duchassaingi | native | ||
| Cardiida | Semelidae | Abra aequalis | native | Atlantic Abra | |
| Decapoda | Nephropidae | Acanthacaris caeca | native | Atlantic deep lobster | |
| Cyclopoida | Bomolochidae | Acanthocolax similis | native | ||
| Macrodasyoidea | Thaumastodermatidae | Acanthodasys caribbeanensis | native | ||
| Ceramiales | Rhodomelaceae | Acanthophora muscoides | native | Purple spiny sea moss | |
| Ceramiales | Rhodomelaceae | Acanthophora spicifera | native | Erect sea moss | |
| Arcida | Arcidae | Acar domingensis | native | White miniature ark | |
| Calanoida | Acartiidae | Acartia tonsa | native | ||
| Isopoda | Leptanthuridae | Accalathura crenulata | native | ||
| Isopoda | Leptanthuridae | Accalathura setosa | native | ||
| Dasycladales | Polyphysaceae | Acetabularia calyculus | native | ||
| Dasycladales | Polyphysaceae | Acetabularia crenulata | native | Mermaid's wine glass | |
| Dasycladales | Polyphysaceae | Acetabularia myriospora | native | ||
| Pantopoda | Ammotheidae | Achelia sawayai | native | ||
| Acrochaetiales | Acrochaetiaceae | Acrochaetium corymbiferum | native | ||
| Acrochaetiales | Acrochaetiaceae | Acrochaetium hypneae | native | ||
| Acrochaetiales | Acrochaetiaceae | Acrochaetium unipes | native | ||
| Scleractinia | Acroporidae | Acropora cervicornis | native | Staghorn coral | Staghorn coral |
| Scleractinia | Acroporidae | Acropora palmata | native | Elkhorn coral | Elkhorn coral |
| Scleractinia | Acroporidae | Acropora prolifera | native | Fused staghorn coral | Fused staghorn |
| Polypodiales | Pteridaceae | Acrostichum aureum | native | Leather fern | |
| Cephalaspidea | Cylichnidae | Acteocina canaliculata | native | Channeled barrel-bubble | |
| Cephalaspidea | Cylichnidae | Acteocina decurrens | native | ||
| Cephalaspidea | Cylichnidae | Acteocina recta | native | Straight barrel-bubble | |
| Actiniaria | Aurelianidae | Actinoporus elegans | native | ||
| Holothuriida | Holothuriidae | Actinopyga agassizi | native | Five-toothed sea cucumber | |
| Actiniaria | Actiniidae | Actinostella flosculifera | native | ||
| Narcomedusae | Aeginidae | Aegina citrea | native | Four tentacled jelly | |
| Leptothecata | Aequoreidae | Aequorea macrodactyla | native | ||
| Miliolida | Hauerinidae | Affinetrina planciana | native | ||
| Scleractinia | Agariciidae | Agaricia agaricites | native | Purple lettuce coral | Leaf coral |
| Scleractinia | Agariciidae | Agaricia fragilis | native | Fragile saucer coral | |
| Scleractinia | Agariciidae | Agaricia grahamae | native | Graham's sheet coral | Graham's sheet coral |
| Scleractinia | Agariciidae | Agaricia humilis | native | Low-life lettuce coral | Lowrelief lettuce coral |
| Scleractinia | Agariciidae | Agaricia lamarcki | native | Lamarck's sheet coral | Lamarck's sheet coral |
| Scleractinia | Agariciidae | Agaricia tenuifolia | native | Thin leaf lettuce coral | Lettuce coral |
| Scleractinia | Agariciidae | Agaricia undata | native | Scroll coral | Scroll coral |
| Neogastropoda | Olividae | Agaronia hilli | native | ||
| Neogastropoda | Olividae | Agaronia leonardhilli | native | ||
| Spatangoida | Schizasteridae | Agassizia excentrica | native | ||
| Neogastropoda | Turridae | Agathotoma candidissima | native | White-frosted mangelia | |
| Agelasida | Agelasidae | Agelas clathrodes | native | Orange elephant ear sponge | |
| Agelasida | Agelasidae | Agelas conifera | native | Brown tube sponge | |
| Agelasida | Agelasidae | Agelas dispar | native | ||
| Leptothecata | Aglaopheniidae | Aglaophenia latecarinata | native | Feather plume hydroid | |
| Trachymedusae | Rhopalonematidae | Aglaura hemistoma | native | ||
| Verongiida | Aplysinidae | Aiolochroia crassa | native | Branching tube sponge | |
| Actiniaria | Aiptasiidae | Aiptasia tagetes | native | ||
| Haplosclerida | Phloeodictyidae | Aka siphona | native |