In the ancient time, the resources were very limited. Thus ancient people learned to use ocean currents and wind in their travels. It was a sustainable process, which lasted many centuries. 

There are several examples that may be usefull for the present time.

Wind can push the ships at a significant speed. For example:

Launched in 1869,  the  tea clipper Cutty Sark  was very famous due to its velocity. The Cutty Sark could reach 17.5 knots [1], and it was considerable one of the fastest ships of the XIX Century, however it was made obsolete by steam engines. 

When the Portuguese explored the South Atlantic ocean [2,3], they found that currents pushed them from Africa, and made them arriving in Brazil.

There are also indications that Portuguese also visited North-America, and the names “Newfoundland”  is translation of the Portuguese “Terra Nova”, and “Labrador” comes directly from the Portuguese name “Lavrador” [4]. The Hamy-King worldmap shows the presence fo Portuguese in North-America near the year of 1500.

Wind and ocean currents were very relevant in Ancient world, as also earlier reported by Homer.

For example, the Odyssey of Homer may, in fact, indicate a  travel to the Ballearic Isands, by means of South France ocean currents. For example, the island of Calypso “Ogygya” in fact can be interpreted as  Ibiza.

The war for Troy is due to the fact that, there is a 5 knot current flowing from the Dardanellos to the Agean Sea. Only in summer this strong current could be overcome by wind [6], and only during few days. The Trojans used to ask tribute and mooring fees [6], making the Greeks discontent. In fact, almost every year there as a war in Troy (and in summer time).

These ancient voyages only were possible due to competent use of wind and ocean currents. 

It is discussed how the competent knowledge of wind and ocean currents could be used nowadays for saving fuel in navigation.