water rockets are typically made from discarded PET soft drink bottles, partially filled with water, pumped with air to high pressure, and released. the water rockets yahoo discussion group is putting together a WR competition.  real simple build and launch a 650ml each two stage rocket, and report your best altitude. video and or pics are needed to verify launch.  no prizes just great fun and bragging rights. designboom readers, if interested can be added to the list ***.  a date hasn’t been established. thanks to lonnie engbrecht for this entry ! *** this list provides a one-stop forum on homemade rockets powered by compressed air and water, and related topics. there are no rules, except to learn while having fun! the list dates back to 1997 with 170 members and 17,000 messages in the archives.