3,400km of French Guiana's waterways are navigable by native boats called pirogues. 460km is navigable by small ocean-going vessels and coastal and river steamers.
There is limited public transport throughout the territory. Minibuses go between major towns but there may only be a few per day. Fares are fixed per route; if only going partial distance to Cayenne you may have to pay the full fare. Eg. St. Laurent du Maroni to Kourou you may have to pay the full fare to Cayenne. Fare for St. Laurent to Cayenne is €50, for Kourou to Cayenne €10, Saint-Georges to Cayenne €40. There is a bus that runs from the airport to the centre of Cayenne, contact the people at the information desk at the airport to be sure the driver stops to pick you up.
There are numerous taxis. They are comfortable but very expensive. A journey from the airport to Cayenne would cost you €35 and the price for a taxi from Cayenne to Kourou could get as high as €85.
There are lots of possibilities for renting cars on the airport and in Cayenne and the other bigger villages.