A hot summer day; Lara is on a vacation in Eagean sea. 

She comes by an allegedly cursed book. Obviously this takes her interest.

The book talks about the castle and treasure of King Triton, son of Poseidon.

Lara searches some of the ruins and after a few unsuccessful raids, she finds
a castle on a remote island. 

Is this the castle she looks for?
Can she find the treasure?
What is this curse people talk about? 
Is that why noone goes to that island?
Is that why noone comes back from that island?