Mizugumo (water spider, a water-crossing device used by ninja) (水蜘蛛)
Mizugumo (literally, water spider) was one of the tools used by Ninja for crossing waters, such as moat or river.
Many of Mizugumo handed down up to the present are footwear, attaching four pieces of wooden float around a geta (Japanese wooden sandal). With this Mizugumo, it is assumed that Ninja walked on the surface of water as if walking on the ground. The wooden float was divided into four parts so that they could be easily carried by folding them. Some original Mizugumo are handed down, but it is impossible for a person to float with them, as the float from the footwear is too small and thus the buoyancy is insufficient. Further, even if Mizugumo are made in a larger size, it is hard to keep a good balance; so it needs some supporting took, such as a walking stick, to walk on the surface of water. In 'All Japan Ninja Championship' organized by Koga-no-sato Ninjutsu-mura (Koga Ninja Village), competitors walk with so huge Mizugumo that they have to open their both legs greatly with a stick as a supporting tool.
It is said that Mizugumo was originally a tool for Ninja to walk unstable surfaces of ground, as kanjiki was (snow-shoes). On the contrary, there is a story that the original size was bigger, like a swimming tube, and Mizugumo was used as a potable boat, but the size was wrongly passed down.