Apple Watch Ultra water lock, swimming or water exposure is not working correctly

The checks in more detail

To end it, turn the Digital Crown, which plays a tone and ejects water from the speaker. If the touch screen seems dead, Water Lock may be on; turn the crown. The Ultra's Action button, the orange button on the left, can be set in Settings, Action Button to start a workout, a dive or other actions, so a press that does nothing may be set for something else. For the Depth app and the water temperature, the watch measures depth and temperature when it is submerged.

Open the Depth app, or press the Action button if it is set to Dive, before you go in. The watch reports a maximum rating for recreational diving, so check Apple's stated limits before you use it, and never rely on a watch for diving without proper training and a dedicated dive computer for safety. If the temperature or depth readings are missing, make sure the watch is dry before the dive begins, the sensors are not covered by the band, and the watch has the latest watchOS.

After swimming, rinse the watch in fresh water, especially after salt or chlorine, and dry it. Use the Water Lock eject to clear the speaker. If a workout does not record, open the Workout app, choose Pool Swim or Open Water Swim and set the pool length. If water mode will not turn on or off, restart the watch and update watchOS through the Watch app. Check Settings, General, Water Lock for the options. If the screen stays unresponsive after ejecting water and a restart, contact Apple Support with the serial number. Treat any diving use with full caution.