This is the 17238th most frequent Russian word.
субмарины
Submarines.
The word "субмарины" here refers to the vessels used for underwater exploration.
Субмарины погружаются на большую глубину в поисках неизвестных существ.
Submarines dive to great depths in search of unknown creatures.
Here, "субмарины" indicates a specific submarine that was submerged.
Учёные исследовали останки затонувшей субмарины.
Scientists studied the remains of a sunken submarine.
In this context, "субмарин" (a form of "субмарины") pertains to scaled-down representations of various submarines.