Underwater atomic bomb detonation at Bikini Atoll - GIF

[Frank S]

With a blast force as great as that apparently was why did the surface of the water remain pristine calm?

[BuffaloJohn]

With a blast force as great as that apparently was why did the surface of the water remain pristine calm?

Much of the initial force was up, that was not calm. Then there was a shock wave that radiated, that was not calm.

With the view being from pretty far away, you just can't see the water fluctuations. Think about it - those are fairly large ships (likely WWII ones - for reference a Fletcher Class destroyer built in 1939 was 370ft long) - obviously put there to test what happens when such a bomb goes off. If the ship is hundreds of feet long, you wouldn't see 20 ft waves or anything like that...