Working on installing shocks in my kayak seat to protect my back when landing flat off of tall waterfalls (necessary when there isn't a deep pool). I can't figure out if it will actually help. I guess you would call this a spring and damper in series problem (the damper being the water). Here's the problem I'm having: Background: When landing flat on aerated water, it is generally assumed the kayak will sink 6 inches into the water reducing the G's and shock of impact. This is usually adequate to protect the back from injury when landing flat off waterfalls up to 20 ft tall (when sitting vertical in the kayak). So, I'm assuming 40 G is the max safe limit for landing with a vertical spine. The same can be done safely from 30 ft if one is tucked as far forward as possible but it will be a very hard landing (60 G?). My goal is to widen the margin of safety by adding shocks to the seat. Problem to solve: If I install springs or shock absorbers with a 2 inch stroke on the seat of my kayak, how do I figure out whether or not that will decrease the G's of landing? For example: If I currently have 6 inches of travel after impact and increase it to 8 inches by adding 2 inch shocks, that would presumably decrease the G's if the rate of deceleration was constant over the entire 8 inches. But I'm guessing it isn't since the springs or shocks will behave differently from the dampening effect of the water. I have no idea how they would work in conjunction. I'm assuming the deceleration from travel in the water is almost constant; but the curvature of the boat means more surface area hits the water as the boat sinks deeper into it, so rate of deceleration should increase somewhat after initial impact. But in general I'm assuming the boat is a blunt projectile and stops as soon as it has displaced a mass of water equal to the combined mass of boat and paddler. What I can't understand is how springs/shocks in my seat would affect the overall rate of deceleration on my upper body from the beginning of impact until I have come to a stop. How could I calculate that? Also, how do I calculate what spring rate to use (or other value if I use a damper) if my goal was to limit my upper body to a certain number of G's? Sorry I'm not a physics person and have limited grasp of mathematics above Algebra II but I'll try to follow if anyone has any ideas.