Cambridge University Library's website has some wonderful scans of artist Conrad Martens' sketchbooks, including numerous images from the second voyage of HMS Beagle (i.e. the Darwin voyage).
Martens joined Beagle in Montevideo in 1833, after the previous ship's artist, Augustus Earle, was taken ill. In many ways, these rough sketches are far more evocative than Martens' subsequent formal paintings.
Shown here is Slinging the monkey, Port Desire, which was painted on Christmas Day, 1833. It depicts Beagle (L) and Adventure (R) at anchor. In the foreground, six sailors play the naval game Swinging the Monkey, which involved hanging one of their number upside down until he was able to beat one of his taunting colleagues with a stick, after which, the two men swapped places.
Apparently, Martens didn't depict Beagle entirely correctly: a pencilled annotation by Captain FitzRoy reads: "Note Mainmast of the Beagle a little farther aft. Miz[zen] Mast to rake more".