There are a number of web sites that provide information from a network of shore-based AIS receivers, mostly around large ports. Many, if not most, areas are not covered by any receivers.
To make matters worse, each network is independent, and only displays vessels within range of their own receivers. So the site that works great in one area may not work at all elsewhere.
We went with the InReach. The satellite network works everywhere and it allows 2-way text when out of cell phone range.