Through my experiment, I found that Soft Pneumatic Actuators (Bellows) with flexible but slightly stiff walls are not severely effected by water depth.

In other words, the displacement of the end of the actuator, as the actuator goes deeper into water, does not reduce as fast as the outside pressure of the F= pgh equation, since the displacement of the bellows I tested were dominated by the stiffness of the walls of the bellows.