True, with a few exceptionsAs I understand it, boaters are actually supposed to monitor channel 16 at all times. Initial "casual" contact is also made on 16, but then both participants agree to switch to another channel for non-emergency communication. There are specific channels for specific types of communication. Check out
http://www.boatus.org/guide/equipment_19.html
On the Gulf ICW, between Galveston Texas, ,and New Orleans La, all commercial traffic, and pleasure craft monitor, and operate on Channel 13. They may stand by on ch 16 also,, but no one is using it.