In the second year of university I created a modification for Skyrim in a team of 3 people. This meant that I had to learn how to use the creation kit released by Bethesda which lets the community make modifications for the game.
The specification for the mod was that it had to introduce a new element of some sort into the game. While playing around with the Creation Kit, we came up with the idea of manipulating water levels in an environment (such as in the water temple in Zelda Ocarina of TIme) but in an outdoor environment, which would create a stunning effect.
The mod also had to incorporate a quest line, so we created a story where the player is sent to a mysterious island with a flooded city. The city is where the player can manipulate the water levels and must do so to be able to reach the bottom and finish the questline.
Although the mod was not 100% finished it was published on the Steam Workshop and is available here