I'm an agnostic. When I was in the service there was no pressure to attend religious services. In boot, we could go to Sunday services or stay in the barracks and have free time.
At sea, we had watches that took priority over religious services. When your watch was over there were small groups that got together, but they were self organised. No official organized services and no Chaplin onboard my ship.
When at sea, maintaining duty watches was priority one, lest we all be praying that we didn't sink and die.