Maupassant is quite candid about what to expect right from the beginning:
This diary has no interesting story to tell, no tales of derring-do. Last spring I went on a short cruise along the Mediterranean coast and every day, in my spare time, I jotted down things I'd seen and thought.
In fact what I saw was water, sun, cloud and rocks and that's all. I had only simple thoughts, the kind you have when you're being carried drowsily along on the cradle of the waves.
Of course he's being a bit disingenuous. In his introduction, Parmee suggests that the diary is best read as a work of fiction as it contains, "many entertaining, largely invented stories and anecdotes: in a word, a superb example of his skills as a short-story writer, with an eye as sharp as his brain." Maupassant is fretful when embarking, irritated by the superficiality and boredom of the society he spends most of his time in. His trip is a form of momentary escape and his "eye" delights in the soothing pleasures of nature, the sea, and the moon. He recounts the stories of people he has known or heard about who could easily populate his fiction: the daring escape of a prisoner, the tragic story of a woman who gives up everything for love, only to discover she has been betrayed. He doesn't spend all his time at sea however, frequently going ashore to hike in the hills or visit towns and observe the people. This results in one rather amusing, prideful exposition on French males being the world's best lovers and conversationalists.
Ultimately Afloat - like most travel narratives - is an attempt to hold the world at bay, however briefly. By isolating himself at sea Maupassant can muse philosophically upon the more miserable aspects of life - war, poverty and death - and momentarily escape them. As a writer though, he knows that humanity is the fodder for his work and however much he dislikes society, he can't stay away for long.
This was a nice mini-break from some of the more serious NYRB books I've been reading.