C'était à la mer.
sea vixon
Sea animals are 'les animaux marins' in French.
A sea otter is 'une loutre de mer' in French.
Ocean in French is "Ocean, or you can use Sea in French "Mer". .
sea shells are coquillages in French. For the purpose of a meal, they are called 'fruits de mer' on the menu.
mammifères marins
mer verte
monstre marin
Une hippocampe
A sea nymph is 'une nymphe de l'océan / une nymphe marine' in French.
"a garden by the sea" is "un jardin à la mer / près de la mer" in French.
sirène par la mer