How??
The MOHO drill stopped at ...
The first attempt to drill to the Moho was in 1961, off the coast of Mexico near Guadalupe, as part of Project Mohole. The deepest hole from that effort penetrated 183 m (601 ft) into the sea floor, the upper 179 m (557 ft) of which consisted of sediments. In subsequent years, only 4 holes penetrated more than 1 km (0.6 mile) into the oceanic crust; the deepest of these was 2.1 km (1.3 mi) off the coast of Ecuador.
In September 2012, a new state-of-the-art scientific drilling ship—Chikyu—surpassed the old record of 2.1 km.
https://www.usgs.gov/observatories/hvo/news/volcano-watch-after-50-years-a-renewed-effort-drill-moho
All ya had to do is read!
Scientists made the findings at the time after studying earthquakes and discovering that seismometers were picking up shockwaves under the surface of the Earth.
From that, they were able to establish that the water was being held in the rock known as ringwoodite.
That expalins it all!