Log flumes (colloquially known as "log rides") are amusement rides consisting of a water flume and artificial hollow logs or boats. Passengers sit in the logs, which are propelled along the flume by the flow of water.
The ride usually culminates with a rapid descent and splashdown into a body of water, which may happen more than once (normally the largest drop being just before the end). It provides people with an entertaining way to get wet and cool off on a hot summer day, with certain seating sections usually being splashed with more water for a more exciting and wet ride. (source: Wikipedia)
Here’s a miniature version of a log flume made out cardboard:
