This page is a walkthrough for the Cayo Perico Heist Preparation Mission, Kosatka. It’ll navigate you through the necessary steps to successfully acquiring the Sonar Jammer
Search Underwater for the Submarine / Locate the Sonar Jammer
Once you’ve activated the mission via the planning board on the Submarine, either use the sub to fast travel closer to the Merryweather Test Site or simply drive there yourself. After you’ve arrived at your destination, head onto one of the nearby islands and take out the Helicopters and Boats from a distance.
Upon clearing out the area, dive deep into the water and approach the Submarines top hatch to enter. Once inside, slowly work your way down to the lowest deck whilst taking out any enemies, then follow the path to the end and you’ll reach the Sonar Jammer.
After you’ve collected the device, exit the submarine and swim back over to the islands. Here you’ll want to take out any Choppers and call your Dingy via the Interaction Menu, then use it to return to the mainland. Finally, take a car and drive back towards your submarine and deliver the sonar jammer to bring this mission to a close.