There's this archipelago of artificial floating islands. These vary in size from less than 10 meters to about 100 meters in diameter.

Is there a passive way to keep them close to each others without the risk of having them collide catastrophically (or, even better, at all)?

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    $\begingroup$ No way unless the vessels are either anchored or else actively guided. Or maybe you could use some rubber fenders. (Note that floating vessels not under active control do not tend to have a long life. The sea is a cruel mistress.) $\endgroup$
    – AlexP
    Sep 16, 2020 at 11:50
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    $\begingroup$ How long do you intend them to be in proximity? How far away from each other would you like them to be? Is a person supposed to be able to walk between any of the elements? Do they have propulsion? Do elements of this archipelago ever swap places or leave the formation? Sorry for being nosy, engineering is like that. $\endgroup$
    – Sean Boddy
    Sep 16, 2020 at 16:56
  • $\begingroup$ @SeanBoddy they are virtually permanently in proximity. From a few meters up to 20 or so. No need for walking. No propulsion (for the sake of the question). Might need to leave formation in extreme cases $\endgroup$ Sep 16, 2020 at 17:43

4 Answers 4


Yes one that has been used for hundreds of years, anchors.

A set of anchors/mooring lines is already a known solution to this, if you use multiple anchors drift is very limited. This is the solutions used by floating oil rigs. There is a variety of arrangements possible depending on what you are trying to achieve.

enter image description here

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    $\begingroup$ what's (g) for? not that I understand (e) and (f)... $\endgroup$
    – carlo
    Sep 16, 2020 at 17:21
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    $\begingroup$ oh wait, (g) is a spring, isn't it? $\endgroup$
    – carlo
    Sep 16, 2020 at 17:25
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    $\begingroup$ @carlo I would guess that in (e) and (f) the buoys are there permanently, but the object being anchored to is not. It might e.g. be a ship that just needs somewhere to anchor but can't use their own anchor (because of depth, currents, ocean floor, whatever). $\endgroup$
    – Graipher
    Sep 16, 2020 at 18:12
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    $\begingroup$ Remembering that each anchored platform will have a swing radius based on the method used and the depth of water. To prevent the issues that ksbes mentions, these circles must not overlap. $\endgroup$
    – Separatrix
    Sep 17, 2020 at 7:21
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    $\begingroup$ @AustinHemmelgarn - Consider an oil drilling platform, which needs to be able to run pipes and tubes straight down into the seabed. Arrangements like (e) and (f) help keep the anchor chain clear of the work area (particularly if you have a style-e anchor on both sides). $\endgroup$
    – bta
    Sep 17, 2020 at 21:11




Your islands are each surrounded by mangrove-like woody plants. Big ones are anchored on the land. Smaller ones are anchored to the big ones and have roots floating free in the water (that is invented here, not how real mangroves work). These aquatic trees intertwine with one another forming dense networks of roots and branches.

This living plant connection absorbs storm energy, just as real mangrove shorelines provide a buffer against storm and wave energy. The roots and branches link the islands with flexible connections. If they break or are crushed in storms, they regrow. If an island breaks loose then comes back and crashes into another island the trees and plants in the way will bend and break, absorbing the energy. The islands will lodge together and immediately the living plants will start growing to bind them.


Underwater bumpers

Well below the surface you could have bumpers with shock absorbers and dampeners.

I made a diagram below.

My diagram of islands with shock dampening technology.

The islands would be like giant aquatic bumper cars that you can live and farm on. As long as the bumpers are underwater and the portion underwater is wider than the portion over water, it will seem to landlubber eyes as the islands never actually collide.

Depending on the (in)efficiency of the bumpers, some seismic activity might result when islands come close to each other.

As an alternative, you may add horizontal rods to each bumper to make sure that they don't have a full collision, but rather literally push each other apart.

  • $\begingroup$ note they will still end up all right next to each other. $\endgroup$
    – John
    Sep 16, 2020 at 19:35

No, thanks to Bernoulli and wind/wave shading large floating object tend to merge with each other.

So if large beams/briges are passive enough for you - it is the only solution.


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