It looks like yes (sort of). "The analysis revealed reservoirs of water at depths of about six to 12 miles (10 to 20km) in the Martian crust." So, they think

It looks like yes (sort of). "The analysis revealed reservoirs of water at depths of about six to 12 miles (10 to 20km) in the Martian crust." So, they think liquid water but it would be hard to get to even if you were well set on Mars with a drill rig. It might or might not need to be purified. They also have not touch water itself but seen indications in seismic data (pretty reliable remote sensing tech I believe).