Did you know that “island” used to be written “iland” before the 16th century? Although an island indeed is land surrounded by water, the word is not written so because it “is land”, but because there is an etymologically unrelated word isle /aɪl/ (pronounced the same as “I’ll”) which also means “island”, and so people during the 16th century thought it would be fun to insert an “s” into the spelling of “iland” as well. Anyway, the pronunciation persisted, and so we still pronounce it as /ˈaɪlənd/.
Also, don’t confuse it with Iceland, the country. “Iceland” is pronounced exactly as its spelling suggests: /ˈaɪslənd/. However, pronunciation of words ending with -land is somewhat more complicated in general; see my article on pronunciation of English prefixes and suffixes.