sandfish vs soft-finned fish

sandfish and soft-finned fish both are nouns.

Word	Noun	Adjective	Verb	Adverb
sandfish	Yes	No	No	No
soft-finned fish	Yes	No	No	No

As nouns, soft-finned fish is a hypernym of sandfish; that is, soft-finned fish is a word with a broader meaning than sandfish:

sandfish: fish of sandy areas of western Pacific and Indian oceans having an angular snout for burrowing into sand
soft-finned fish: any fish of the superorder Malacopterygii

Other hypernyms of sandfish include malacopterygian.

sandfish (noun)	soft-finned fish (noun)
either of two small silvery scaleless fishes of the northern Pacific that burrow into sand	any fish of the superorder Malacopterygii
fish of sandy areas of western Pacific and Indian oceans having an angular snout for burrowing into sand