Just want to document my recent experience visiting Hainan visa free as there isn't much information online (many information are also outdated).

Visitors from 59 nations can visit Hainan visa free up to 30 days with following restrictions.

You must stay within Hainan province, which means you must fly non stop to and from Hainan. (Arriving in SYX and depart out of HAK or vice versa is ok, you cannot connect via another Chinese mainland city). If you want to travel to another Chinese city outside of Hainan, you must go to immigration office to apply for a permit.

You don't need to apply ahead or contact any travel agency, just show check in staff and Immigration official printout of the hotel and flight reservation.