While you can't add a third person, you can significantly enhance your 2-player sessions with these recently updated mods: Stranded Deep's 20 New Items! (2024 Mod)
As of early 2026, still officially supports a maximum of two players for both online and local co-op. While community members frequently request 3-4 player support, no functional "3-player mod" exists that reliably bypasses the game's hardcoded engine limits. Current Multiplayer Status Official Limit : The game remains capped at 2 players . stranded deep 3 player mod updated