San Andreas is the first game in the series that allows you to swim with your character, meaning that water isn’t instant death like in the previous ones. You can also dive underwater, which is done by pressing Circle (PS4)/B (Xbox)/A (Switch). Of course, you can only stay underwater for so long, as you have a breath meter, which will be located underneath your health and armor. In order to get this trophy/achievement, you have to drown, so stay underwater until your breath meter is gone, which will then cause your health to decrease. Once all of your health is gone, you will drown.