BorderGuard seems to be working in a way because I get craploads of lag when I get too close. I did get to -2900 unintentionally (was going to plant a marker on the shallow land right around there, but lag caused me to change my plans), but I immediately turned back.
Anyways, west of Kaeshar, beyond that rainforest, theres nothing but ocean and scattered islands. Even went north quite a distance within the 1000 mark and didn't hit land. I'm in the open ocean right now and its nighttime.
I wasn't really trying to push the limits with the -2900, I was at around -2800 something, saw a bit of shallows nearby and wanted to put down a marker of some sort. Was going to turn back from that point anyway.
Edit: What the? Server disconnected me for thinking I was moving too quickly, however I (or the server) was having lag pretty badly at that moment. I was in a boat at that time as well.
Edit2: When I logged in, I was next to land and what I guess happened is that the server registered me as having crashed the boat, but I was still away from land and hadn't registered the crash.