This page of the trophy guide for Far Cry 6 explains how to unlock the Jawson Brody trophy. To get it, you have to kill a shark with an explosion. This can be done in a variety of ways; below, we have included an example method of easily killing a shark with an explosion.
We recommend getting a tank for this method. You can find out how to obtain one on the page Tank - how to steal?. Remember that you can steal a found vacant tank or sabotage and take over a tank that's driving around.
Use the tank to drive to any beach by the ocean on the world map. Park the tank on the beach and exit it.
Take out your smartphone and use it to "scan" the water. You should eventually spot a shark, which will automatically be tagged.
Return to the tank's cabin and use its main cannon to shoot at the shark. Eventually, the shark will die and the trophy will be unlocked.