Swelfish or Swellfish: How To spell?
The word Swelfish is misspelled against Swellfish, a noun meaning "Any plectognath fish that dilates itself, as the bur fish, puffer, or diodon."
Swellfish has double "ll" is mispronounced as "l"Remember double 'LL' in between the strings swe & fish which should not be misspelled with single 'L'
Wrong Spelling:  swe-l-fish  Correct Spelling:  swe-ll-fish 
Find more wrongly spelled words of Swellfish to spell it well.