Start the mission with the Jaeger-7 sniper rifle waiting in the ICA Safe House (building to the right of the Villa's main gate). Grab the sniper and leave the safe house through the bathroom. Walk along a thin ledge over to an open window leading to the kitchen. Sneak past the cooks, out to an open patio, then follow the cliff-side around the next building.
Follow the path until you see a guard leaning on a railing. Distract him with a coin and continue down the path on the right. There will be another guard along this path, so be ready to take him out. Continue down to a short wall facing the ocean.
With the rifle, look for a lone boat in the distance with 4 bells on it. Shooting these bells, in the right order, will summon the Kraken and unlock your achievement!
- First one is halfway up the left most sail.
- Second is on the very front of the boat ( I don't know the proper boating terms).
- Third is on the top of the middle sail.
- And the fourth is in the right side of the cabin.
Let me know if you have any questions.