It is called the Bermuda Travel Authorization. Pretty much thirty days before your arrival, they will list your ship and time in port on their website. You then register each person, provide proof of vaccination, and send them a $40.00 payment per person.(It was $75.00). They then send you your "authorization" to visit the island. Every person entering their waters has to have one, whether you set foot on Bermuda soil or not.
There are literally hundreds, if not thousands, of posts on CC over the last year or so about this subject. You just need to do some research. Happy Sailing!!