In Hydrophobia the player takes the role of engineer Kate Wilson who works on the cruise ship Queen of the World. Unfortunately terrorists took over and placed bombs all over the ship and after detonating them chaos breaks loose. Now Kate has to fight for her life.

In this environment water plays an important role and it emphasizes realistic water representation. Water is the main component in many of the game's puzzles in which Kate uses her kinetic powers, gained in the second half. Other puzzles involve using an universal device to hack security installations (as a mini-game) or find out codes to open doors. Those are written in an invisible font on walls and have to made visible with her tool. The rest of the game consists of climbing sections and shoot outs with terrorists. Here the game uses a traditional cover system and five ammo types.