The interior honneycomb structure is made of cellular concrete, which can be drilled and sawn like wood. Here is one way the raw cell array can be cut away to form a living space. The traditional western style of architecture is to have a hallway of doors to single-entrance rooms. A hexagonal symmetry lends itself to highly connected rooms adjascent to common areas.
One drawback is the absence of windows. Only modules on the perimeter of the aggregate could have windows with a horizontal view. Skylights are always an option. 'Sealights' are an interesting possibility, bringing in outside light along with an underwater view. Any kind of windows pose an added risk of flooding and would have to be much more rugged than buildings normally require. Adding and maintaining underwater or partially submerged windows once a module is launched will present a challenge. One alternative to windows into the module is to build a 'sun-room' on the top surface, perhaps combined with the entrance stairwell.
Here is one way to build an entrance. A spiral staircase leads down into the foyer, which has several doors to the rest of the structure. The top surface of the module is seven feet above mean sea level, so some waves may wash over it in heavy weather. The module is highly bouyant, so most of even a large wave will pass underneath. Excluding the remainder is the major issue in designing an entrance. The example shown uses a 'conning tower' approach. This could be carried further by raising the outside door several feet above the top surface. The ultimate in protection would be to use a double-door 'airlock' on the landing at the top of the spiral stairway.
Another form of entrance is to raise the lental, and cut away part of the floor in one of the rooms to give sea access, and an emergency 'back door'.
