[Elladan and Elrohir]

This is slightly off-topic, but it just occurred to me. One of the wild adventures Bilbo mentions is "visiting elves". Yet we know from "The Quest of Erebor" that Master Baggins himself visited elves prior to Gandalf's visit (in fact, he was off celebrating the Elvish New Year the first time G came to call on him!). Obviously, that work was written decades later, but is Tolkien intentionally making Bilbo hypocritical?

And, on the subject: I don't know that we can say the "sailing" was just something that the hobbits made up. At any rate, Bilbo, at another point in the conversation, is a reliable witness: he poetically describes Gandalf's fireworks, and is affirmed by the Grey Wizard. And, of course, you have the case of Isengar Took, already mentioned earlier in the thread. I think Hobbits did go to sea in some fashion.