Originally Posted by two stroke mick
Are ribs known as pontoon boats in the States?
Sort of. Even my buddy who owns a 15.5' Zodiac calls his boat a pontoon boat (he also smokes enough dope to kill a herd of cows, though, so his normalcy is questionable.)
A pontoon boat, properly, is sort of like a raft made of 55 gallon drums: It's usually 2 welded aluminum flotation chambers (kind of banana shaped) under each gunwale, onto which a flat deck (or in some cases, 2 tiers of decks) is/are fixed. They are usually outboard powered, but occasionally will have inboard engines.
They're known for being slow, lake-cruising type vessels, but I've seen some that will do better than 40 knots, and had an acquaintance who ran one in Monterey Bay for diving (4 to 6 foot swell, couple of feet of chop.)