The story as recounted by Hamlet in a letter to Horatio shows us a different side to his character, one more devious and calculating than we're used to. We already know that Hamlet is not the kind of man who'd immediately grab hold of a sword and head off to run Claudius through. This is a thoughtful, intelligent young man, somewhat prone to introspection. If Hamlet is going to carry out his revenge, he's going to take his time about it; and when it finally does happen, it'll show signs of having been thought through carefully beforehand.

When Hamlet realizes what his old school chums, Rosencrantz and Guildenstern, have been up to, he becomes more determined than ever on avenging his father's murder. Again, he won't just rush into things; there's plenty more brooding and indecision to come. But the steel has entered into Hamlet's soul, as can be seen from the almost casual way he sends Rosencrantz and Guildenstern to their deaths in England.

By this stage in the play, most of the audience is probably wondering when Hamlet is going to get started in putting his revenge plot into effect. There must also be a general skepticism as to whether Hamlet has either the guts or resolve to see the whole thing through. But such doubts are—partly—dispelled by Hamlet's devious actions aboard ship. At least now we can see that his character is more multi-faceted than we'd been previously led to believe. Whatever we may think of Hamlet's behavior towards Rosencrantz and Guildenstern, there's no denying that we're suitably intrigued as to what's going to happen when the young prince returns to Denmark.

Before Hamlet gets on the ship, he begins to use his innate intelligence to discern the true characters of his former friends, the turncoasts, Rosencratz and Gildenstern. He compares them to sponges "that soak up the King's countenance,/his rewards, and authorities.../When he needs what you have gleaned, it is but squeezing you, and sponge, you/shall be dry again" (4.2.15-21).

When he embarks on the forced journey (ordered by Claudius), Hamlet hears of the movements of Fortinbras and begins to wonder about himself. First, he thinks about how reason alone separates men from beasts: "What is a man/If his cheif good and market of his tim/Be but to sleep and feed? A beast, no more," he proclaims (4.4.35-37)

While biding his time on the ship, Hamlet challenges his own intergrity and bravery. He knows the time has come to act to avenge his father, punish his mother and uncle, and halt Fortibras encroachment:

I do not know
Why I live live to say "This thing's to do."
SIth I have cuase, and will, and strength, and means
To do 't. Examples gross as earth exhort me..." (4.4.45-59).

By the time the story of the ship concludes, Hamlet has strengthened his resolve to act on his principles.