The two letters that create the digraph in the word “fish” are “-sh”. A digraph, for those who don’t know, is simply a sound that is made when two letters are put together that resembles the sound of a single letter. “-Ph”, “-ey”, and “-gh” are good examples of other digraphs that are common in the English language.
The double “L” in Spanish that sounds like the letter “Y” is an example in a language that isn’t English. The digraph is simply a language thing. There’s really nothing that makes it any more special than having a letter repeat in a word. There’s nothing wrong to identifying it, and there’s simply nothing to stop someone from identifying it unless they don’t know what it is.
