Ok, now I have two serious problems.
1.- Can I use SDL_gfx for rotation? This way the shark can rotate in any arbitrary angle. Other way the shark should pass through some predefined angles 0-45-90 etc...
Using sdl_rotozoom is way too slow for real time Dingoo usage. But it's possible not to use it realtime. You have to use precached. Rotated images and preferably not for the whole 360 degrees. For example use sdl rotozoom to create 60 surfaces of an image increasing the angle 6 degrees and display the surface wich comes nearest to it. Wel rotozoom is useable. That way without problems on the Dingoo! I already used it
2.- The shark movement is also a problem, for example, if I use UP to move the shark up (like in the ecco games) , will have an unrealistic behavior while flying.
If I use the UP key to rotate the shark, like in a motocross game, then the shark flying will be ok and backflips could be done, but then while swimming the shark would swim upside down, and I have never seen a shark swimming that way.