Yes, the army has done amphibious ops. They learned how from us. During the 1920s and 30s, the Marine Corps developed the amphibious operations manual. We wrote the book, the same book the army used also. We developed the doctrines and the tools for forcible entry on defended beachheads and the army also uses it.
The Army has always done amphibious operations, long before the doctrine that emerged in the 20s and 30s.