"e3_seafloor" is a Half-Life 2 Beta map shown at E3 2003. This map was replaced by d2_coast_04 in Half-Life 2. On this map, Gordon is pursued by a Gunship that he must try to flee. Many Combine Soldiers patrol the docks. They must be killed using the Tau Cannon attached to the Buggy. Gordon eventually finds a rocket launcher near an armored vehicle. It allows to shoot down the Gunship which crashes on the road. Fade to black.
Hey, are you the guy that uploaded that music supposedly from the Counter-Strike: Source alpha on Youtube? You've both got the same profile picture. What happened to that video? Is it a real piece of music from the alpha, and if it's legit can you upload it somewhere on Youtube again?
I'll reupload it soon! :)