I assume this works similar in premise to how someone can generate forward momentum by pumping a hydrofoil surfboard like this https://youtu.be/3Ksamgpu2S0

But it looks like this boat isn't using a foil, but rather hydraulic pump based electrical generators inside the boat. The article is short on details on how the design works. They do link to two other foil based propulsion boats though:

https://www.popsci.com/gear-gadgets/article/2008-02/wave-run...

https://newatlas.com/autonaut-autonomous-unmanned-surface-ve...