There are very few hotels on the island. So it makes sense to live in the neighboring St. Thomas island and make daily boat trips to St. John island.
How to get there 
Fly to St. Thomas airport (STT)
. (In most cases, it will be cheaper to fly via San Juan airport (SJU)
.) Get by shuttle bus from St. Thomas airport to Red Hook
ferry pier. Next take a boat to Cruz Bay
of St. John island.
When to go 
Any time of year. The winter half of the year features by the greatest number of tourists on the island.
Water temperature, C
Wind speed, meter/sec