I also built a Python AIS parsing library with a bunch of command-line tools (e.g., aisgrep, ais2json): https://github.com/wpietri/simpleais
If anybody ends up using this, please let me know. On Twitter, I'm @williampietri. I have also been keeping a copy of all the AIS data for the last few years, and am happy to share it.
The sort where I could subscribe to notifications and get a few messages a day and go "huh, that is cool".
Ships like you describe are also often weirder with what they transmit. Cargo and cruise ships go from known port to known port in reasonably predictable ways. (Reasonably predictable meaning that 50 or so regexes can usually extract a little sense from what some sailor types into a bridge console.) But a lot of data from smaller, less predictable ships is much less regular.
Now that it has been running a while, I should definitely go back and see what else I can extract from the data. But one of my problems is that this stuff is poorly documented. What I really need is connections to maritime experts who can look at the data and say, "Oh, that ship is..."
I should say this isn't all AIS data, just all that comes through this particular network of receivers. For truly global coverage, there are satellite AIS receivers, but I don't have access to that.
E.g., do you need line of sight? I'm a couple km from water, not quite 100m elevation.
AIS technology works similar to ADS-B, but the details of being on the water make reception a different problem than for planes. There's three or so major ground-based AIS tracking services out there that compete, and while AISHub isn't the biggest it is the most open.