It is recommended for the player to create a shelter to survive in survival mode. Shelters are completely up to the player; they can be made out of any materials, span any size, and take on any shape. The player should note that a shelter is better to be made out of an inflammable material, such as stone, bricks, or stone bricks, for it isn't uncommon for fires to accidentally start. It is also recommended that the shelter is lit well with torches or redstone lamps, as one would not want monsters to spawn within the walls. Most shelters have some sort of door too, otherwise mobs or monsters may stray inside.
Here are examples of possible shelters.
A house that's underwater so ALL monsters drown. I do NOT recommend because you can drown and the bed gets soggy ;).