What is this?

[BigV]

You're right!

It's a water rocket launcher. Fill a one liter plastic water bottle halfway, put the cork in the mouth of the bottle and lower it onto the latches. The red hose is connected to a bicycle pump. Pump it up to about 80 - 100 psi, then pull the string which releases the locking arms. Whooooooosh! My rocket sucked. Nobody likes an acrobatic rocket, but you do make the highlight reel. The best perfoming rocket had a hang time of about twelve seconds.