Altimeter Epix Pro gen 2 51 drop when contact water

That's expected. The elevation is measured with the help of a pressure sensor, and any amount of water in the sensor port will cause a sudden increase of the sensed pressure, hence a strong drop of elevation.

Barometer rises up at the time of the contact of the water, and slowly descending back to normal for about 5 minutes., but this is very disturbing at the time of hiking elevation drop to minus, and has an effect on the elev gain. my fenix 7 have not this problem. maybe have same problem, and how to fix it..i think this problem after firmware update last night.

I've had this problem for a long time, even holding the watch on the left side with the sensors facing my hand, when I wash it the altimeter 20-30 meters down and comes back up after just half an hour. I don't know how reliable it is with sweat; I've never tried to do a test.

for me its ok when not activity use, but this is very disturbing at activity like hiking.

its broken barometer sensor or normal case..my wife watch Quatix 7 pro and normal when contact splash water like rain or just washing hand..

It is normal behavior, but it may slightly differ from model to model (depending on the size and position of the sensor port), and can be algo aggravated if the sensor port is dirty, or with some debris in it.