is, as Baggins Babe says, identical to the description of his arrival at
Valinor at the end of RotK (book). Non-readers could be misled by the
movie's use of this lovely text to describe the afterlife; Valinor is a very
real, physical (though fictional!) place inhabited by living elves and (for a
time) at least two live hobbits. This dream is obviously a forshadowing
of Frodo's eventual sailing to Valinor.
The other dream sounds like the Grey Havens. As lucia mentions, there was
a palantir there, but it was only capable of looking West. The longing
for the sea is indeed curious in a hobbit, obviously some more foreshadowing.
A more striking vision occurs to Frodo in Lorien, in Galadriel's mirror.
I'm sure you'll recognize its contents. What's curious about that vision
is it includes things that actually happen but not to Frodo and Sam (or
anywhere near them). It also ends with the voyage to Valinor.
Almost certainly it's the Ring that's enabling these dreams and
visions.
sic hobbitur ad astra.
(Entire text of a postcard received by JRRT in 1937, according to Letter #17)
