Forerunner 935 does not support diving, and the pressure sensor is limited to the pressure equivalent to 3 m on almost all watches not supporting diving. Diving is supported on the Descent models, and on Fenix 8
Edit: There is perhaps a chance an old model like FR 935 does not have the 3m sensor limitation, but Garmin does not permit apps for diving in the Connect IQ store. You would need to side-load a 3rd party IQ app to test whether it is the case or not. Perhaps the app at https://www.apnea.me/ could work for that purpose.
