Yeah sure you're technically correct, but consider the context here... we're comparing a Mars vehicle to a vessel that's literally submerged in an ocean. Gettin

Yeah sure you're technically correct, but consider the context here... we're comparing a Mars vehicle to a vessel that's literally submerged in an ocean. Getting drinkable water on Mars isn't nearly as straightforward as it is on a submarine. Drop a submarine on Mars and you could be hundreds of miles from easily usable ice. You have to be careful about perchlorates and it's either soil- or ice-locked.