Can I actuate soft robots in other fluids (eg: water instead of air)?

Soft actuators behave similarly for air and water, as long as the right pressure is provided. 

However, for the control board, switching from air to a different working fluid might required alternative components and specifications. The pump we list is meant to use air, so you would require a different pump to achieve the required pressure. The pressure sensors/manifolds we use are also meant to be used with air so you will have to find alternatives.