The notion of finality seems to drive Tennyson's work. If there are any moral implications to the poem, it resides in the last stanza. It seems that Tennyson is arguing that one has to be able to face their "Pilot" as the sum total of their doings. In this confrontation, the idea would be that one would be clear of behavior that is less than dignified or actions that cannot be defended. As one moves to this level, there seems to be a heightened responsibility towards ethical actions and moral behavior because the condition of "Crossing the Bar" demands it. Individuals are placed in a different setting entirely when doing this and such a movement necessitates acting on a different and more elevated level.
The moral lesson of this poem is that we should not fear or mourn death because when we die we are going to meet our "Pilot" -- we are going to meet God.
We see this theme in the second half of the poem more than in the first. In the second half of the poem, the speaker asks that there should be no sadness of farewell, that people should not mourn his passing. He says that this is so because he will meet God when he crosses the bar.
The first part of the poem has a different message, but one that is less to do with morals, in my opinion. In the first part of the poem, the speaker is hoping that his death will be easy -- that the weather will be good for the voyage.