A raft is a vessel or structure that's made to float on water. You might have an inflatable raft you use for floating around your backyard pool.
Rafts come in many forms, from soft and squishy to wooden and permanent, like the rafts built on lakes for swimmers to rest on and dive off. Other rafts are mobile — they're small, flat boats meant for transporting people or goods across a river, for example. If you raft, you travel by raft. Experts guess that raft comes from the Old Norse word raptr, "log."