In the Caribbean islands in general and Antigua in particular there is no requirement for insurance; some marinas require proof of insurance in order to dock or store the boat there (Jolly Harbour in Antigua has such a requirement, for example). Clearing into Antigua is a bit onerous, as an ex-British colony they tend to be sticklers for procedure. I know of an acquaintance who cleared in with a Delaware-state-registered boat, but as mentioned above a lot can depend upon the immigration official.
When clearing in you will need your outbound clearance papers from the prior departure country, the boat ownership papers and passports for all on board. If you clear in at English harbour there are 4 "desks" that you will need to present yourself and papers in the correct order. The first desk will give you a bunch of forms to fill in, once that is done you'll then be allowed to the immigration desk where you'll get 2 more forms per person to fill in, once that is done you return to have immigration clear the people in, then return to the initial desk to get the boat (almost) cleared in, then to the Parks desk to pay your mooring/anchoring fees and then finally back to the first desk in order to complete the whole procedure. If one is well-kept and polite the procedure is painless but can take 30 minutes or more when the office is empty. I keep on thinking back to one time with a French gentleman in front of me who made the mistake of stating "They don't do it that way back in France" and his sojourn in the immigration offices took hours longer than mine