The juxtaposition is riveting. Above the waterline, the waves are so big, they're pushing you backward, rolling you up, and slamming you into the shore. Below the waterline, you barely hear them roaring above you, surrounded by a peace and calm and serenity.
Much of religion has been spent trying to get rid of waves - waves that have come and gone for thousands of years, sometimes bigger, sometimes smaller, but always there.
I think that's why religion is often found so empty.
Spirituality/enlightenment/nirvana seem to accept the waves and, instead, teach us to hold our breath a little longer so we can go underwater when they come.
I think that's why it's often found much more fulfilling.