Theory on wave energy
on the internet there are good sources of information. One of the best teachers on this subject is professor Falness from Norway. The university that has many years of experiance is the university of Eddinburgh. Professor Salter is one of best on this subject.
A more recent book is 
other publications.
Presentation; Wave energy design (Fred Gardner / Miguel Prado)
Wave energy (edinburgh university)
An education site on wave energy
Wave conversion devices (some examples)
HBO duurzaam 