The latest image on google earth is with low tide. Most of the sand you see on the image gets flooded creating a larger body of water...You must walk some feet into the water to get some depth, but it adds quite some space knee-waist high... and then you fall into the river. There is a shipyard inside the river so it is dredged from time to time -they once dredged so much the famous wave at Mundaka dissapeared, although its back again-. Since the river is deep, it carries a great volume of water -mostly salt water from the sea- therefore the most noticable currents are tide currents, which are really strong at the end of the river since it is the narrowest spot, plus the sea side has nice waves to surf and -since the river is dredged- it usually adds the rip-current to the tide current. Not a nice place to go for a swim.
Most of the windsurfing at spain is done in the south or at the mediterranean sea (More than 700 Km away from my house). I took my lessons at Formentera, which is quite far away and the boards are all the Start L and the maximum sail size for the school would be 5.5m (As I recall since my teacher asked for a 6.0 or 6.5 in order to try to hook in and there was none). Hope there was a bit more of windsurfing at the north, as it would be great to test some boards and get the feeling... But there's no chance. That's the main reason I keep asking in order to keep my money save, as I shall buy the equipment at an online store and get it shipped.
I've visited about 20 online stores at spain -not including the islands due to shipment expenses- and none of them got the Rio M. Only one of them has replied he could get one from a school, but he told me he wouldn't recomend it since it has some damages. Some reply they have the Start L, but I see it hughe to carry on the roof of the car plus I really think it probably has a low lifespan. Most of the used equipment is the Tabou Rocket or Naish Kaluha, which seems easier to find on the stores but I haven't seen one live, so I'm not too comfortable buying something I haven't seen live. The Rio and Go, I haven't tried them out but I've seen them live, and it gives me some security on what I'm buying. However, most of the used equipment I've found are board with volumes under 140 liters... even some online stores won't sell new boards with more volume than the Go 144. It seems that where most of the people sail, they rent until they've got reasonable skills and then they buy a board. Once again, this is not possible where I live
I'll follow your advice and keep dry until I can find a Rio M.
Thanks for your advice.