hull-down

adjective2

1. •
   Of a ship: so far distant that only the masts and sails are visible above the horizon.

   • In the morning a homeward-bound ship passed us hull down,—the first we had seen for months; […] — 1898
2. •
   Of a tank: stopped with its hull protected by ground to the front, so that its occupants or weapons have a line of sight forward.