we do not have the technology to go to the bottom of the Marianas Trench.
Except we reached it four times since 1960 : https://en.wikipedia.org/wiki/Mariana_Trench#Descents
Except we reached it four times since 1960 : https://en.wikipedia.org/wiki/Mariana_Trench#Descents
However, if you assumed that we were able to go the bottom of the ocean, transporting supplies there would be much easier than transporting supplies to Mars.