1. You are welcomed to check out [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=14.0]Transverse Wave and Longitudinal Wave[/url]
2. What really important is relative motion.

For object moving in a fluid:
if you change your system to moving with object , then the object is at rest and the fluid is moving.

Please check out [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=140.0]Relative Motion (frame of reference)[/url]