Well, Puerto Rico is not a country itself, but even still Cuba has the longest coastline of all three.
Cuba
In order of largest to smallest island (and therefore longest coastline to shortest coastline) 1) Cuba 2) Jamaica 3) Puerto Rico 4) Trinidad
Cuba is the largest, followed by Haiti, Jamaica and Puerto Rico (in that order)
Cyprus, Lebanon and Jamaica
Cuba, Jamaica, Hispaniola, (Haiti and Dominican Republic share the island) and Puerto Rico
He was born in Kingston Jamaica.
Cuba Jamaica Puerto Rico Hispaniola
Estimated time from Jamaica to Puerto Rico is 703.67 miles
Yes you can.
189 miles
If you are a US Citizen no Passport is required for Puerto Rico, but it is required for Jamaica.
Since it is a Caribbean Island it must have a coastline.