Using seismic activity to probe the interior of Mars, geophysicists have found evidence for a large underground reservoir of liquid water—enough to fill oceans on the planet’s surface.
It’s located in tiny cracks and pores in rock in the middle of the Martian crust, between 11.5 and 20 kilometers below the surface. Even on Earth, drilling a hole a kilometer deep is a challenge.
Not to rain on your parade but:
https://phys.org/news/2024-08-scientists-oceans-mars-deep.html
Ain’t nobody getting to that water anytime soon.