Waterproof cases are designed to protect electronic devices such as smartphones, cameras, and other gadgets from water and other liquids. While waterproof cases can provide protection against rain, splashes, and accidental drops into water, they are not necessarily designed to work underwater.
Most waterproof cases have limits on how deep they can be submerged and for how long. The limits vary depending on the specific case and the manufacturer's recommendations.
Additionally, while waterproof cases may provide a tight seal to prevent water from entering into the device, they may still be subject to pressure changes that can negatively impact the functionality of the device. This is especially true if the case is exposed to rapidly changing water pressure, such as in the case of diving.
To summarize, waterproof cases may work well for protecting electronic devices from water damage, but they are not necessarily designed for use underwater. If you plan to use your device underwater, it is best to look for a specialized case that is designed for that purpose, or to research carefully to ensure that the waterproof case you choose is appropriate for the specific conditions and depths you will be using it in.