St. John is largely a do it yourself vacation destination - packing a cooler, beach chairs, snorkel equipment and heading out for the day is the norm. You absolutely need a vehicle and to get to some of the more secluded beaches, and up and down the steep hills/road grade when it is raining - a Jeep. Vehicles are in short supply due to unprecedented levels of travelers to the USVI so book asap - it may be difficult finding one even now.

You will be driving to the beaches - there aren’t many accommodations on beaches in St John - especially sandy beaches. Many cottages and villas are on the hillsides to take advantage of the spectacular views. Most condos are in town (Cruz Bay). I would start a villa search here:
https://stjohn-villarentals.com/ This site connects renters and owners and you can avoid paying fees.

I suggest checking out the St John TripAdvisor forum. Great community and tons of info.