A tsunami is not only a high energy wave . In deep water ( where submarines are lurking ) , the wave has a high speed and a long wavelength , but a very low amplitude . The ocean surface only a few centimeters can oscillate up and down .
It is only when the wave reaches shallow water slows, heaps upon itself , and dramatically increases in amplitude .
A submarine in deep water would not be affected . A submarine near the coast can be destroyed by being smashed on the shore .
Actually, I think that nothing would happen .
My math teacher in sixth grade was actually in the ocean ( out ... she was in a kind of tourism dive / snorkel trip or something) when the tsunami hit India and its environs , and I feel nothing . The tsunami really dangerous part is when it breaks . If you are in the water before the water level rises right .