I made this as a potential idea to how humans can live underwater in remote locations. It is an underwater living space with a bed, toilet, and small fridge (Everything you need to survive). It is a small room that is made of a hollow half-sphere anchored underwater with a hatch leading to an above-water platform with a small motor boat.

Supplies

Tinkercad
Creativity

Step 1: Create & Hollow Out a Half Sphere

Place a half sphere on the grid and scale it up to a large size. Place a second sphere and scale it up slightly smaller than the first. Turn the second one into a hold and center both half spheres using the align tool. Group them together and change the color to one you like.

Step 2: Create a Bed, Toilet, and Fridge

To create the bed take a cube and change it to appealing dimensions. Then copy and paste it to create a similar cube, shorten this one, and make it white to act as a pillow. Align the two cubes to form a mattress, pillow, and sheets. Lastly, make a small platform underneath the bed to act as a bedframe.

To create the toilet take a cylinder and change the size to make it stretched and short. Then copy and paste it. Take the copied shape and make it taller and less wide. Align the two shapes to create the toilet.

To create the fridge take a cube and change the dimensions to make a realistically scaled. Then create a handle using another cube.

Step 3: Create Anchor

To create the anchor take a tube from the shape bar. Make it taller and skinnier. Then copy and paste it into 4 tubes. Use the tubes to make a chain then get an anchor from the hardware bar. Add the anchor to the chain and you're done with that.

Step 4: Platform With Boat

To make the platform you must get a cube, make it flat, and make it wider and longer. Once you do this you also have to make a tall hollowed-out cylinder above the room leading to the platform as and entrance and exit.

To make the boat you take a pyramid shape and shift it 45 degrees to one side. Take a hole block and cut the pyramid down the middle. Once you do this rotate the half pyramid to be one point down. Then copy and paste it into another half pyramid. Take this other one and scale it down just slightly then make it a hole. Align both half pyramids and combine them.