Sailing without wind, but with strong currents

Context

On my world, there is a lot of water: sea, oceans, ... There are also firm land and islands, so it's interesting to travel on the water. The problem is that there is NO wind at all, and lots of currents. These currents are mostly tidal: basically, they go in one direction for some time, then in the other for nearly the same amount of time, at more or less the same speed. It is hence impossible to practice normal sailing, the boats would just be moved around by currents and getting nowhere but reefs.

The technological level is equivalent to what was available on earth during the 17^th century.

Question

The boats must be able to choose where they are going, and not merely be moved around like cork would be.

I'm thinking about two possibilities, but I am unsure if these are viable:

• Use an anchor when the current is not going where you want to go. (Problem: it's difficult to move sideways from te current).
• Reverse the concept of a boat: use small "sails" underwater for propulsion, and enormous sails in the air to steer and prevent drifting.

Is there a possibility to use the currents in order to move a boat toward its goal?

posted over 6 years ago

Legisey‭

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