Looks like An accursed sea dog (until he reconstitutes as a skeleton) except he's much more active. He will whirl around the beach area and reconstitute as a skelly for just a few seconds and then resume his whirling.
Strategy[]
Wavewreck the Reckless has an effect where players standing close to him will take damage from the bones spinning around him. The further away from him you are, the less damage this effect does.
At 51% health, Wavewreck the Reckless will briefly become non-aggro and change into Wavewreck the Abominable