Half-Life: Before
A small single-player mod for Half-Life with new maps and a new story. The mod is built on Spirit of Half-Life 1.8, which has greatly improved both its visuals and its functionality.
You play as a scientist from the Black Mesa complex. All the action takes place on a large cargo ship somewhere in the middle of the sea. A scientist with a squad of marines has holed up in the captain's bridge, while the ship's deck has been overrun by alien creatures. The game begins as you land on the ship's bow from a helicopter.
The mod is completely free. You can download it from one of the following sites:
Screenshots: