My point being that the draft of the tension leg platform, regardless of depth beneath the platform, has to be related to the expected wave height. If wave drop exceeds the draft point where the platform is positively buoyant, then you have unacceptable movement. This means there is a minimum size/draft of a tension leg platform.
Doesn’t matter the depth, if the wave height exceeds the buoyancy line in a negative direction, you could still get a wave drop that exceeds the balance of buoyancy vs tension. Once you lose tension, you have a good chance of exceeding design tolerances on the tension anchor/line on the upward rebound, not to mention uneven vertical acceleration. At a very minimum you get an abrupt deceleration at the top (abrupt jerk to a stop.)
In my previous example above, I over-simplified, but the idea is that I get at least one foot of play for the platform to vertically accelerate upward before being stopped by tension. X tons moving a foot/second doesn’t like to stop abruptly.
A more precise example would have included details about total weight, vs total volume and determined where the buoyancy line is in terms of draft. Bottom line, if your water line drops low enough to loose the tension on the platform legs, you get unwanted movement and abrupt deceleration again back at the top, which is dangerous to platform and occupants. Thus the minimum draft/buoyancy ratio of the platform is dictated by the wave height design parameter. You have to have enough draft volume to maintain buoyancy without moving vertically at the maximum expected wave drop, ad enough freeboard to be above water at the maximum expected wave height. Thus there’s a minimum hull draft for a tension leg platform under given conditions.