When I was working on West Indian English, there were not many observations that I made that were really original. But one that was concerned the semivowel w. I noticed that in Jamaican (and often no doubt in other Caribbean varieties) it has a labial-palatal allophone [ɥ] before front vowels, thus wheel ɥiːl, west ɥes, swim sɥɪm, etc. As far as I know, no one had noticed this before.
As with various other features of Caribbean English, this characteristic can be explained as due to a West African substratum.
In Akan (Asante Twi) of Ghana, to quote Wikipedia,
Before front vowels, all consonants are palatalized (or labio-palatalized) […and the plosives are to some extent affricated]
The name of the language, Twi is accordingly pronounced tɕɥi.
Although the labialpalatal semivowel allophone made it across the Atlantic, the affrication did not: Jamaican twist is tɥɪs, not *tɕɥɪs.