First, You have to look at the structure of "Pelamis Wave Power Technology"
1) You can see, it contains "Three Power conversion modules" so they convert the power in another direction, hence, minimize the effect to marine animals.
2) It contains anchors, which makes it so flexible so when wave comes, and it causes the Pelamis to rise and fall in a snake like motion, so protect from waves.
Hope this helps!
