I love my Ribtec 9m, which seems (to me at least!) very well designed and balanced, such that the tubes are just off the surface at rest, and so don't pick up much growth or wear, but do help provide stability with only a very little movement on either side.
Especially for a boat left afloat for long periods I wouldn't want them submerged all the time, but then again, don't like the idea either of some RIB's where they are so high off the water they provide very little stability in most use cases.
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