The Tower Vault Heist

From publisher blurb: A Pathfinder Compatible Adventure for 3rd to 4th level characters. With notes for a follow-on adventure for 5th to 10th level characters. This adventure is designed to be placed and run in any fantasy setting. A tower has sunk under the waves, with only the top still being accessable. A mysterious letter holds the key to breaking into the tower and penetrating the security to reach the treasure vault at the bottom. Can the players sneak through to steal their prize and then fight their way out or will the tower's security defeat them?