It all depends on what the pool is made of for example: concrete? thickness? etc.
The mass of the contents of that pool, however, can be calculated if the contents material is known: water? air? etc.
It depends on how long the pool is.
If the 25 meters is a circle, it would be 68256 gallons
10 x 20 x 1
a pool, a building, the ocean.
It would take 64 m3 of water, which is 64000 liters or about 16,907 gallons.
However long and wide you want to dig it.
meter
That depends upon how large the swimming pool is.
Approximately 29,640 US gallons or 24,680 Imperial gallons.
It is 3 metres deep and 50m long
Long Course
It depends... how long, wide, and deep it is.
In a long course meter (LCM) pool, 50 meters equals one length of the pool. In a short course meter (SCM) pool, 50 meters equals 2 lengths or one lap of the pool.
Assuming 25 meters is round. . . . 123449 gallons.
An olympic swimming pool is 2m deep, 50m long and 25m wide.
A 50 meter butterfly in a meter pool is if the pool is a 25 meter pool then it's doing the butterfly down and back.
Figure out how many cubic meters it holds. A cubic meter is 1000 liters, so go from there.