The protagonists are shown travelling in one vehicle during an interior shot near the start of the episode. When the convoy arrives at the hanger they exit from different vehicles.
Dahlia states she will sink the submarine in the Mariana trench where it will cause the nuclear warheads to vaporize the submarine. The Mariana trench has a relative pressure of 1000 atmospheres at its deepest point. Nuclear weapons require pressure a pressure of around 400,000 atmospheres to achieve fission. The devices would not achieve fission and not vaporize anything.