In Minecraft, if you ever desire to get rid of water that is present within a given area and have realized that simply placing a block in the source might not get the job done, it’s time to look at another specific item. That specific item would be the sponge - an item that can get rid of and hold in water.
Where To Find It
You cannot craft a sponge in the conventional sense so you will have to find it.
Your best chance would be to search deep within ocean biomes for certain large structures that contain a great deal of sponges. These particular structures are called Ocean Monuments, and besides being inhabited by certain guardians and elder guardians, you can also find rooms full of sponges for you to mine.
Just take care to be wary of these guardians, for they fill these ocean monuments to the absolute brim whilst patrolling the inside and outside of the structure you seek. The Elder guardian in particular can be a nasty piece of work to deal with if you are unprepared, and especially fast if it happens to get outside of the monument itself. If possible try and avoid it entirely so as to avoid any unnecessary risks unless you're equipped to deal with it.
The best tool for you to use in order to get the largest sponge yield and to do so most efficiently would be the hoe. In every sponge room there will be around thirty sponges for you to take, so be sure you're getting your time’s worth.
How To Dry It
The sponges that you get from the Ocean Monuments will more likely be wet and unable to absorb any other source of water if you desire it. From being in the ocean they will have water already filled within and thus will be unable to take on any more liquids. If you wish to dry it out a simple solution is present for you. All that you will need is a furnace and a fire source, preferably coal due to its efficiency and longevity.
There are other unorthodox methods that are available if you desire it. A sponge for example will dry out in certain climates if present within them. Within the nether realm if you were to place a wet sponge within, it would dry out almost instantly in a puff of steam and revert to a normal sponge. The same thing happens to a lesser extent if it is placed in a dry biome where it will dry out over a set period of time. Even if a sponge absorbs water in a dry biome it will not take long for it to puff out steam and revert back to its original state.
Examples of Dry Biomes are as follows.
Sponges are a rare yet useful tool if you wish to rid a certain area of water for your own personal uses. The most difficult part about a sponge is acquiring it from the ocean, so take care not to lose the ones you acquire if possible.