>Make your depth 50ft.
>Zero bubble.
Bubble: The up or down angle of the boat, with a “zero bubble” being an even keel. The bubble may have to be changed to maintain depth. For example, if the ship is getting heavier as it’s making water, or lighter due to pumping sanitaries or any other myriad evolutions, you may have to pitch the ship’s nose down to stop from rising or pitch it up to stop the boat from sinking. The ship could also be out of trim fore to aft, not only heavy or light overall. The Diving Officer of the Watch is responsible for keeping the ship in trim. Rarely do you have a zero bubble; right around a ½ degree up is fine and at periscope depth you actually want an up angle of 1, 1.5 degrees or so depending on sea state. This up angle at periscope depth accomplishes several things: it keeps the screw from broaching in case you suddenly pitch down (the screw can’t do its job if it’s in the air and not the water), it keeps the scope clear, and it keeps the expanse of the ship aft of the sail lower, thereby lessening suction upward by wave action (because of the Bernoulli Effect).
https://en.wikipedia.org/wiki/Bernoulli%27s_principle
In fluid dynamics, Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluid's potential energy.12 The principle is named after Daniel Bernoulli who published it in his book Hydrodynamica in 1738.[3] Although Bernoulli deduced that pressure decreases when the flow speed increases, it was Leonhard Euler who derived Bernoulli's equation in its usual form in 1752.[4][5] The principle is only applicable for isentropic flows: when the effects of irreversible processes (like turbulence) and non-adiabatic processes (e.g. heat radiation) are small and can be neglected.
Bernoulli's principle can be applied to various types of fluid flow, resulting in various forms of Bernoulli's equation; there are different forms of Bernoulli's equation for different types of flow. The simple form of Bernoulli's equation is valid for incompressible flows (e.g. most liquid flows and gases moving at low Mach number). More advanced forms may be applied to compressible flows at higher Mach numbers (see the derivations of the Bernoulli equation).
Bernoulli's principle can be derived from the principle of conservation of energy. This states that, in a steady flow, the sum of all forms of energy in a fluid along a streamline is the same at all points on that streamline. This requires that the sum of kinetic energy, potential energy and internal energy remains constant.2 Thus an increase in the speed of the fluid – implying an increase in its kinetic energy (dynamic pressure) – occurs with a simultaneous decrease in (the sum of) its potential energy (including the static pressure) and internal energy. If the fluid is flowing out of a reservoir, the sum of all forms of energy is the same on all streamlines because in a reservoir the energy per unit volume (the sum of pressure and gravitational potential ρ g h) is the same everywhere.6
Bernoulli's principle can also be derived directly from Isaac Newton's Second Law of Motion. If a small volume of fluid is flowing horizontally from a region of high pressure to a region of low pressure, then there is more pressure behind than in front. This gives a net force on the volume, accelerating it along the streamline.[a][b][c]
Fluid particles are subject only to pressure and their own weight. If a fluid is flowing horizontally and along a section of a streamline, where the speed increases it can only be because the fluid on that section has moved from a region of higher pressure to a region of lower pressure; and if its speed decreases, it can only be because it has moved from a region of lower pressure to a region of higher pressure. Consequently, within a fluid flowing horizontally, the highest speed occurs where the pressure is lowest, and the lowest speed occurs where the pressure is highest.[10]