Minecraft hardcore, buffet ocean map.
You get one life, and you start in the ocean. If you're lucky, damn lucky, there will be a spit of land nearby. Most maps I've never seen land above water. Most people wimp out quickly on these maps. lol
Find a sunken ship with a door. The door makes an air pocket. Make more doors.
You can place a block on top of kelp, meaning you can start building at or near the surface. Lots of land spawns lots of mobs and animals.