Shakespeare's The Merchant of Venice opens with Antonio, the Venetian merchant of the title of the play, talking with his friends and fellow merchants, Salanio and Salerio. They're trying to determine why Antonio is feeling so sad.
ANTONIO. In sooth, I know not why I am so sad;
It wearies me; you say it wearies you;
But how I caught it, found it, or came by it,
What stuff 'tis made of, whereof it is born,
I am to learn... (1.1.1-5)
Salerio seems to sum up Antonio's emotional state at that moment.
SALERIO. Your mind is tossing on the ocean... (1.1.8)
The imagery in Antonio's dialogue with Salerio and Salanio about Antonio's sadness relates exclusively to ships at sea.
Salerio says that Antonio must be concerned about his many merchant ships, and his mind is at sea with his ships. Salerio paints a picture of majestic ships at sea, sails full and banners waving, sailing effortlessly past less impressive ships.
SALERIO. There, where your argosies, with portly sail,—
Like signiors and rich burghers on the flood,
Or, as it were, the pageants of the sea,—
Do overpeer the petty traffickers,
That curt'sy to them, do them reverence,
As they fly by them with their woven wings. (1.1.9-13)
Salanio remarks that if he had as many ships at sea as Antonio does, he wouldn't be thinking about anything else.
SOLANIO. Believe me, sir, had I such venture forth,
The better part of my affections would
Be with my hopes abroad. (1.1.15-17)
Solanio says that he would be checking the direction of the wind and looking at maps, constantly worried about what might go wrong with his ships.
SOLANIO. I should be still
Plucking the grass, to know where sits the wind;
Peering in maps, for ports, and piers, and roads:
And every object that might make me fear
Misfortune to my ventures, out of doubt
Would make me sad. (1.1.17-22)
Salerio adds that everything he looked at would remind him of his ships at sea. His breath cooling his soup would remind him of a wind blowing his ships off course.
SALERIO. My wind, cooling my broth,
Would blow me to an ague, when I thought
What harm a wind too great might do at sea. (1.1.23-25)
The sand in an hourglass would remind him of ships running aground on the beach, their masts broken and fallen into the sand.
SALERIO. I should not see the sandy hour-glass run,
But I should think of shallows and of flats;
And see my wealthy Andrew dock'd in sand,
Vailing her high-top lower than her ribs... (1.1.26-29)
As a side note, "wealthy Andrew" is a reference to the San Andrés, one of two large Spanish ships that were captured by the English during the Cadiz expedition in 1596. This reference helps to establish that Shakespeare wrote The Merchant of Venice between 1596, the time of the capture of the San Andrés, and a reference to Shakespeare and The Merchant of Venice in a book written in 1598.
A stone church reminds Salerio of the "dangerous rocks" which could break open the sides of his ships and throw their cargo of silks and spices into the sea, making his merchandise worthless.
SALERIO. Should I go to church,
And see the holy edifice of stone,
And not bethink me straight of dangerous rocks,
Which, touching but my gentle vessel's side,
Would scatter all her spices on the stream,
Enrobe the roaring waters with my silks,
And, in a word, but even now worth this,
And now worth nothing? (1.1.30-37)
Salerio says that thinking about these things would certainly make him sad and no doubt has the same effect on Antonio.
SALERIO. I know, Antonio
Is sad to think upon his merchandise. (1.1.40-41)
Antonio ends Salanio and Salerio's speculation about his concern for his ships. Antonio says that he hasn't put all of his money and merchandise into only one ship going to only one destination and that his wealth isn't entirely dependent on his ships currently at sea.
ANTONIO. Believe me, no; I thank my fortune for it,
My ventures are not in one bottom trusted,
Nor to one place; nor is my whole estate
Upon the fortune of this present year:
Therefore my merchandise makes me not sad. (1.1.42-46)
At this point in the dialogue, the imagery of ships at sea ends with Salanio's definitive assessment of the reason for Antonio's sadness:
SALANIO. Why, then you are in love. (1.1.47)