How does Patrick O'Brian use imagery in The Nutmeg of Consolation?

Imagery:

The seventeenth, and the Nutmeg barely had her lower masts in: her beautifully dry, clean, sweet-smelling holds, scraped to the fresh wood by innumerable coolies and dried, all hatches off, all gun-orts open, in the last fiery parching blasts of the previous monsoon (not a cockroach, not a flea, not a louse, let alone rats, mice or ancient ballast soaked in filth) were so empty that she rode absurdly high, her bright copper showing broad from stem to stern."

"Richardson stood high on the yard, looking down into the clear water ahead, dark blue for the deep water of the channel, light for the shoals on either side."