Symbolism in Crossing the Bar

Initailly, uopn reading this poem I thought it was literal: a man out at sea. But, with a hint from the questions following the story, I quickly began to understand the real meaning. I think he compares his trip into the ocean to life, starting with Sunset and ending with Twilight. What really made me understand the meaning of this poem was the God symbol at the end. He says, "I hope to see my Pilot face to face/ When I have crossed the bar." The God reference rang a bell because we always talk about seeing God "face to face" when we enter heaven and the fact that God is the Pilot that guides us to our place in the afterlife. The speaker speaks of his death as one of peace that he hopes will not bring mourning. But, what doesn't make sense is how is crossing the sandbar like death? I don't really get the whole sea metaphor.