Super Mario Sunshine

What do you mean by "boards"?

Yoshi can walk on everything except water. If he touches the water he "dies".

I don't really understand what you mean but if you mean where do you find him in delfino plazo it is on the house with the melons under the green roof thing you can bounce on and there is the wood tower with the bell on top and you have to bring yoshi a fruit of his choice (the picture of the fruit he wants will appear in a cloud above his head) when you bring the fruit to him he will come out of his egg and you can ride on him. Yoshi can walk on everything except water however, he can survive in a small pool of water for a while but if you leave him his juice flows quicker and he will die. If you leave yoshi on dry land without any fruit near him he will run out of juice and die as well however, if you leave him near a piece of fruit he will auto-feed himself when his juice gets low. You can press the B button and yoshi will stick his tounge out and he can eat things and when he eats fruit he will turn a different colour. If you press A and the control stick yoshi will spin jump and can spit juice everywhere with the R button. He can also do many tricks while spraying juice.

I know yoshi is on Biancco hills, Ricco harbor, Pianta village, gelato Beach, Pianta park, and sirenna beach; which levels i don't know