Sculptures of Nagare Botoke (‘Flowing Buddha’) were votive offerings made to Buddhist deities in Heian-period Japan to ward off diseases and plagues. The figures were in single-block technique, with no facial or specific body details, and were then left floating in rivers. Hinoki wood is very light, and highly rot-resistant. Villagers rescued the sculptures from the waters, and then worshipped them as sacred images in their shrines. Very few are known to have survived, and those that have remain in the local shrines where they were placed a millennium ago.
I am indebted to Dr Riccardo Montanari for this information.