(Another blandly silly Victorian costume idea: the octopus hat! I feel there's a real possibility for a whole group of ocean-themed costumes: mermaid, sea maiden, salt water, and, of course, gem of the ocean! Being more practical than the sea maiden, this fish costume has legs.)
Costumes of this kind can be carried out in scaly cloth, the fins of gauze distended with wire. The head-dresses representing the head of the fish. The skirts short with high leggings covered with scales. A cod, a sword fish, an octopus can be so represented; for the latter, the various feelers form the head-dress.
Holt, Ardern. Fancy Dresses Described, Sixth Edition. London: Debenham & Freebody, 1896.
The 1896 edition of Holt may be found online at the University of Wisconsin Digital Collections.