At displacement speeds (1 to 3 knots), volume produces a lifting force. At planing speeds above 3 knots, volume no longer produces any lifting force. I'm sure some here will still argue the physics of it, but if there is not water on top of the board, then there is no displacement force acting on the board via the displaced volume of the board. As soon as the water slides off of the back of the board and is no longer on top of the board, planing forces are producing 100% of the lift with no additional lift from volume. The problem with having volume in a tail is that it puts your foot further away from the planing surface. This creates a longer lever arm and gives the rider less control over the planing surface beneath them. Getting your feet closer to the planing surface under the board is what gives you more control. Being able to "sink the tail" has nothing to do with how much volume is there if you're moving at planing speeds.
This is correct when considering your average board design, but the nose and the tail are not the real reason why these boards are tough to get up wind with. Rocker and rails together can do more than nose or tail shape. Flatter rocker, and harder sharper rails, on a pointy nose to pointy tail board will make it better at getting up wind more so than not having a pointy tail or pointy nose. Large fin set is also tremendously helpful.
These moves still do not involve buoyant force from volume. In order to shift from planning forces to buoyant force, water needs to be on top of the board, or at least up the sides as far as the equivalent displaced amount of water to produce that buoyant force. The second you actually sink the board, you are now in a position where you have too much drag to get going anyway. Wave power alone will not get a submerged board moving without an extreme cost in time and control of that start. Reducing your ability to get going is not a trick in surfing, any more than coming to a stop is a trick in walking.
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