Rowers are especially interested in tidal currents if they are rowing outside of Richardson Bay, e.g. around Angel Island. The tidal flows in the Bay create vigorous rip currents, areas of faster flow and turbulence, at points where the flow is restricted, curves around a land feature, or collides and mixes with other currents.
When waves run into water moving in the opposite direction, they are slowed, just as if they were approaching a beach. Wave length becomes shorter, wave height higher, and they may break. A good (bad) example of this is an ebb current flowing out of Raccoon Strait into waves coming in from the Golden Gate. Good rough water training, if that's what you want.
Like trail runners and mountain bikers, open water rowers value the variety and challenge of the “open trail”, or in our case, the “open bay”, and the chance to experience nature while getting exercise. Open water rowing also tends to be more inclusive of recreational rowers and less driven by competition.
Using the term "open water" rather than "recreational" rowing does not intend to deny or discount the presence of those many who row entirely for the pleasure of the sport, it merely applies a name to a new and rapidly growing area of the sport which more accurately describes its characteristics and possibilities.