I love windytv. I am a pilot and use it often.
I am also an avid kayaker, sailor, and scuba diver in the Puget Sound (Salish Sea) and Canadian Coast. It would be tremendously interesting/helpful to create a similar web page, but for tide currents instead. Kind-of like your wave option.
One factor/parameter that would make it interesting are the river flows (fresh water dumping into the Sound). As a scuba diver, I can tell you that they influence the currents and visibility significantly.
Also, knowing/seeing how the currents are affected by depth ... and to understand how the horizontal and vertical eddies are formed and how strong they can be come would be very interesting/helpful.
I would love to learn how to code this kind of predictions/simulations for tidal currents. I am an Aeronautical Engineer, and have been involved with modeling aerodynamics for airplanes, for a long time.
Thank you, for your thoughtful consideration.