Is Lightsaber hilt Resizeable?

IS LIGHTSABER HILT RESIZEABLE ??

I saw in Episode 1 that when obi wan kenobi and qui gon jinn follow jar jar binks into water (River) to his city, they hold their lightsaber in mouth and that time size of lightsaber hilt is too small then actual ( like ballpen or like that ) and When they come out, Size of lightsaber hilt was actual as before. Also Same thing happen when Order 66 was executed ( Episode 3 ) and colne shoot Obi wan (utapau) and he fall into river and when he came out, lightsaber hilt's size was small.

Now Other Question come out...

WHY LIGHTSABER HOLDER BELT NOT WORKING IN WATER ?

As we see that whenever they are in water, they hold lightsaber in mouth, and in normal case they put lightsaber to their holder belt. Why they avoid to use belt in water for hold Lightsaber ?