A
watch with condensation under the glass needs to go to authorized
service center without delay, even if the condensation disappears again
after a short time. This is one of the worst things that can happen to a
watch.
Water might have enter the movement through the unlocked (pushed
back) crown that went unnoticed. Water can also penetrated the case but
the seals are still tight enough to prevent it from evaporating.
There are a few ways water can sip into the watch:
1. watches that have not serviced for more than a few
years whereby the lubricants has dried up.
2. presses the watch's buttons when watch is under water.
3. watch's crown did not push in.
4. Watch is wet while it is on the wrist, didn't wipe off the watch in time.
5. Swim with watches that are not 100m water resistant.
6. watch went through sudden change of temperature, eg. out from super hot summer weather into cold room.
However, all watch brand's warranty does not cover water condensation.