You are supposed to get the visa to the island before going to 

the French island of Martinique

. Other tourists from our cruise ship didn’t have it, but they came ashore without any problems. 
We rented a taxi ($30 per person) and went to see the local Pompeii. The Volcano St.

Pele 

incinerated the city that had been settled down at the foot of the mountain.
Here’s the volcano and the ashy black beaches of 

Martinique

.
Of course, we stopped at the farm where the rum is produced. 
We even drove through the rainforest. Do not expect anything stunning, there are a typical forest and a waterfall which is more like a streamlet. There is simply nothing else to see.
There is no need to take a tour to two Pitons, two mountains of the "unearthly beauty" could be easily admired from the ship.