Due to the HCP concept, the island will be a kind of fractal shaped hexagon. Arms can be tethered off the coast, as long as the tether/gangplank can take the torque exerted on them by the loadings on the plank and the islet.
I used this to test the calculations that returned 144 bottles per layer per metre square, and was pleased to find the count gave me 144.5 per metre square. In the above each circle is either 1 Pet bottle, or one Hex cell. The tether and the gangplank are just added for show, as they are not really overlapping far enough for the needed rigidity to be possible. A curious effect I noticed during experimentation was that if some of the edge cells were left flooded, or partially flooded, the stability of the system appeared to increase. This is useful for the creation of artificial beach areas and storm breaks, as the water depth can be tapered downwards from the waters edge, allowing areas with a few feet of water and perhaps sand, before the deep ocean. This would act as a solar collector, and the water on a sunny day would be markedly warmer than the deep sea beyond its limits. This effect could be used to enhance the OTEC system using standard thermal pumps. It would also enhance the system for the tourists!
The actual shape of the colony would be up to the overall planners and the permissions given. Once in place the cells would have to stay in place until officially moved, simply for reasons of stability, both of people’s minds and the top-heavy loads. The underlying structures could all be run easily. The water supply travels via standard 1 inch mains high pressure plastic water pipe, under the surface, then sprouting up when and where needed. Once the demand from one area became too high for the supply of the single pipe, another would be routed by frogmen to the far end of the current run, so allowing further growth. Precise metering of each pipe would prevent fraud and tell of leaks without any problems. How much water goes in the suppliers end is the same as the, for example, five users get out over the same period. Any shortfall would indicate fiddling the meter or a leak. These would be flagged up by computer for investigation.
Electric power would work on two voltages. Standard a.c. would be on 240 volts, where it was required with a limited supply of 3-phase in those few areas that require it. Most people would simply use a high current d.c. 24Volt supply which is tapped from the main 240 supply. All modern computers, rechargeable drills, laptops, mobile phones, etc, will all cope with 24volts or lower, changing down as needed. Backup power for nighttime would be stored by each person separately using either two lead-acid batteries or other storage systems. This will prevent the need for the generators to run all night as well as all day. The low voltage system would prevent electrocution and allow everyone to remain free of the problems of reliable electricity supply. Powerful heating will not be needed due to the sunny climes the city-island will be situated in. Once the OTEC system is de-bugged and operational, this will, of course, no longer be a problem, and we will have lots of free electric and lots of fresh water.
Another thing which would be of immense practical value would be a pneumatic tube delivery system. While these have largely fallen from favor, for point to point delivery of things such as post to physical locations such as between two post offices, they are brilliant. Unlike terrestrial systems, ours would be very low cost and very high efficiency, using hard plastic, continuously drawn and totally air-tight tubes. Provided the bend radius is kept large enough when the system is installed, there is no reason for this system not to be as reliable and low maintenance as all our other systems. As it would be routed below the surface, bend radius could easily be kept large, physical space is not a problem, and access for any repairs would be as simple as every other system on Oceania.