>>53969076Its very simple. You either build from below the water and expand up into the water (with the hassles that provides) or you build a solid dome and hollow it out. You can make an air pocket with 6 blocks. Use the same air pocket principal to obliterate all of the water inside the rest of your structure until you're airtight. Also, build in compartments so when a new section you're building floods, it doesn't flood the whole structure.