Answer:
Depth of the submarine = 668.09 feet
Step-by-step explanation:
From the figure attached,
In triangle ABC,
Distance between a navy cruiser and a nuclear submarine = 2500 feet
Angle between the water level and the submarine = 15.5°
By applying sine rule in the given triangle,
sin(∠BAC)° = 
sin(15.5°) = 
BC = 2500[sin(15.5)]
BC = 668.09 feet
Therefore, submarine is 668.09 feet deep in the sea.