What sort of announcements do the Coast Guard announce on the Marine Radio?

What does the Coast Guard announce on the Marine Radio band apart from emergencies?
Please let me know, thank you.

Listening to Marine Band radio

I have a marine band radio, and I like to listen in to boats and ships at sea.
I have discovered that I can hear Coast Guard stations well enough, but when a vessel responds to the shore station either I cannot hear it at all, or else the remote signal is too weak or garbled [...]