That's a single-masted Phoenician galley Jonah and the sailors are on. I learned a lot about them here and cribbed the design mainly from this tile by nineteenth-century tile designer William de Morgan, who had a thing for ships; also, delightfully, a team of sailors, shipwrights, and historians of various kinds recently built an authentic replica Phoenician galley, so I was able to look at photographs of one, which I had not expected to be able to do. But Eyeteeth, you ask, how did they steer that thing? There's no wheel! I lucked out there in that Phoenician galleys employed steering oars, which meant one less thing to draw, because I figure the sailors wouldn't be using them in this situation.
As for the text, here's where shit gets real. Have I mentioned that I find the Book of Jonah hilarious? Jonah has got to be the worst prophet who ever lived, which I think is kind of the point: that whoever you are, however much of a whiner or a chunkhead, God can use you and he will use you so you'd better be ready to go when you're chosen. Don't be like Jonah here, who is so self-absorbed, so spiritually clueless, that he is about to sleep through the wrath of God. The captain of the ship has to wake him up to pray, which all the other guys on the ship are already doing -- which is the first indication of what is going to become my favorite thing about this episode, the highly sympathetic portrayal of the non-Hebrews. It seems safe to say that Jonah is the only Hebrew on the ship: his people weren't sailors, and he appears to be the only passenger. (Maybe Jonah fled by water because he figured the god of his agrarian people wouldn't think to look for him on a ship among a bunch of Phoenicians and Assyrians.) But all those foreigners are already doing their spiritual duty, calling upon their various gods; it's only the Hebrew, the most chosen individual among the Chosen People, who has to be woken up and told to pray.
Consider Jonah's mission: he has to go to Nineveh and preach to it specifically. The sailors are going to be impressed in a few minutes when they witness the power of Jonah's god, but impressing people of other nations is incidental. Generally, they are to be left alone to worship however they want -- it's not Jonah's problem if they want to worship other, lesser gods. In fact, he is clearly the asshole here for putting them in the path of his god's anger. We'll see in a couple of verses that they repay his disregard for their lives with a regard for his that he has in no way earned. So as I see it, one of the lessons of the Book of Jonah is that people whose beliefs differ from your own can be good, and that you can maybe even learn a thing or two from them about being a good person. And that it's a dick move to endanger people's lives, even if those people aren't from your tribe.
Man, I love this book more and more. It's funny! It's profound! The protagonist is a total jackass who gets swallowed by a fish!