In Tennyson's "Ulysses," whom does Ulysses address in the second half of the poem?

The
speaker, , is addressing his fellow sailors. He calls out to them directly as "my
mariners," and states that both he and they are now "old." Because they are all
old, Ulysses suspects that his mariners will share his views, and particularly his fears about
what is yet to come for them. He appeals to the sailors, telling them that although they are not
young men any more, it is not yet too late for them to do something else "noble"
before they die.

Ulysses' appeal to his fellow sailors is intended to
encourage them to join him on his voyage, a voyage which will be their final one. He
incentivizes the sailors by suggesting that they may yet meet again their old friend, Achilles,
in the Happy Isles, and find a "newer world" beyond the stars before the metaphorical
sun sets on their lives for good. In the stirring and oft-quoted final line of the poem, Ulysses
exhorts his fellow sailors to join him in this quest: they may no longer be as strong in
physical terms as they once were, but they still have the strength of will "to strive, to
seek, to find, and not to yield."