Putting logs in running water (such as a stream) prior to air drying is a way of seasoning timber. Look up Water Seasoning:
WATER SEASONING.
Logs are often stored under water. The tendency to crack that exists when they are exposed to the hot sun, and the danger from insects and from rot, are counter acted as long as they remain thus submerged.
Woods keep safely under water, and, at the same time, undergo changes that render them more durable after they have been removed from the water. They dry rapidly when brought again into contact with the air, and are then durable in proportion as they have been washed by the water. Water seasoning is usually combined with natural seasoning.
The water acts, first by excluding the air, and second by leaching out impurities. There is no reason why wood should ever decay while it remains under water. The softening or physical disintegration that may eventually take place is not decay. Logs are sometimes found buried deep in the mud of swamps. Pieces cut from such logs are often particularly prized because in the course of immersion they have been so thoroughly cleansed and rendered durable, and also because they have lost much of the natural tendency to warp.