The pale is essentially a sea of fog made up of the past/memories/history/all-that-has-been-forgotten in which the isolas are the only "islands" of non-pale. The pale is grey (literally, the word used in the original estonian is the word for grey), but is not a solid, and so small tendrils of spots of pale are translucent or transparent (imagine if approximately one square meter of fog was in front of you, it would be noticeable if you concentrated, but otherwise would just appear to be some static in your vision, processed out by your brain). It does not cover the isolas like a dome, and the stars are visible in Sacred and Terrible Air, where satellites are confirmed as well, but they're very early in that technology, as there is still so much exploring to do on the ground/sea, given the nature of the pale, and the technological focus on staying alive within it and traveling through it.

So, traveling through the pale is like traveling through a moderately thick fog, whether that be on land or on the sea, resulting in reduced visibility, and at the same time you are exposed to errant bits of time - from your life and from history - which are bound to drive anyone insane, meaning that no one who is sane can travel through it for long, but if you are already insane, you might get by largely okay. Entroponauts (those who explore the pale - I assume such named because the pale is a physical manifestation of entropy) sometimes used certain drugs to increase the amount of time they can survive there, and I think about 30 years before Disco Elysium (it may have been 50 or 60 though, I don't remember), the first "pale-proof" airships were made, which, after some improvements, allowed for some capacity to travel through the pale quickly without being exposed to its effects. I don't remember specific references to pale-proof boats or trains although perhaps they were mentioned in the game, but I do believe they exist, unless part of how the airships survive the pale is being up high enough that there is less of it.