If your dive computer suddenly breaks down in water or becomes unusable due to a dead battery, stop the dive immediately and start ascending at the maximum ascent rate specified by the dive computer.
The maximum ascent speed of a typical dive computer is 10m per minute.

After ascent, refrain from diving or boarding an airplane until nitrogen has completely drained from your body.
Six times the maximum tissue halftime given in the diving computer's operating instructions is the time required for nitrogen to completely be discharged from the body.
The maximum tissue halftime used on a typical dive computer is 360 minutes (6 hours) or 720 minutes (12 hours), so 36 hours or 72 hours is need to be watched.