Beaches allow more physical distancing than rivers. I believe the government understood it would be unfair to restrict Dominicans access to the beaches, while allowing tourists inside hotels to have access to them. It could backfire for the tourism industry.
As Alter Ego says, few tourists go to the rivers, probably those only on adventure travel excursions.
As Alter Ego says, few tourists go to the rivers, probably those only on adventure travel excursions.