USVI to BVI

I thought I read that if you are fully vaccinated that you could fast trip to BVI ?

I am not quite sure what you mean in your post but currently no vessels are allowed to enter the BVI other than the two ferries per day currently approved.

Define fast. No day trips, although BVI residents can do day trips to the USVI. From the USVI, you would do a PCR test, apply to the portal, take another PCR test when you arrive, and wait 24-48 hours in an approved quarantine location. Then you would need to fulfill the USVI requirements to return there. There is talk about switching to rapid tests.