I assume you mean "A" sea slug. No, a sea slug is not a fish, but an echidnoderm.
If you mean PROTIST, then no.
A slug is a mollusk like a snail, if you mean a slug like from a shotgun about length of shell, slug can also be slang for bullets which can be literally any size up to max.
To move or act slowly - as a snail or slug does.
rifle slug regular slug
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Swallow shot slug
Roz is voiced by Bob Peterson .
"Sluggish" means slow, or labored, or moving like a slug.
a slug looks weird and has a slimey coatingLike a slug