Forbidden Island is an excellent introduction to co-operative board gamng.
The 'board' is created by laying shuffled tiles (never the same order twice) to create the island. During the gameplay, the tiles get turned over once to show they're being flooded and it's the players' role to ensure they are shored up to stop them being removed forever.
There are four treasures to collect before the island sinks, and it's up to the players to work together to collect the treasure cards, the treasures and then get to a specific tile (Fool's Landing) before playing a Helicopter Lift card to complete the game.
The game mechanic is similar to Pandemic (same author, Matt Leacock). The one starting tile layout is shown in the instructions. I recommend visiting BoardGameGeek and checking out the forum threads for a translation of the German instructions that have a few more challenging layouts, and a printable A4 page with plenty of even more callenging layouts from it's wide fan base, should the original layout ever become stale.