The water right under the bastion shouldn't be there. There should be a gap. The water itself: You could mix two materials together using a "picture filter". Make the second material totaly tranceparent. You must make the picture yourself, but it's easy, just draw long black lines on a white background. Foam: Make a landscape with a big hole in the middle. Choose the white material. Make it 100% tranceparent and use one of the filters and adjust the filter until you got tiny white dots. Copy the landscape, make it smaller and adjust the filter so you get larger dots. This way you get several layers with white dots. :)