1. The first of the seven other seas is initially difficult to distinguish from the more commonplace seas near its entrance, which some say is in the North Pacific. Navigation, however, is almost impossible. One can usually tell that one has entered the first other sea by the complete malfunction of GPS, compasses, celestial navigation, etc. at the same time. At night the stars are blurry smears across the sky. Generally the advice to those who have entered an other sea is to get out as quickly as possible, so the navigational problems pose a grave difficulty and few people have come back from the first other sea. Because it is near the North Pacific Gyre, great washes of plastic are sometimes seen near the entrance and this can be a way to navigate out. The nature of its actual hazards is rather vague. Some speak of just escaping the rising of unusually violent storms; others of drifts of fog they felt compelled to avoid. One must assume those who did not make it back learned somewhat more.
2. The water of the second sea is sweet and cherry-scented. It falls in extravagant waterfalls from steep, rocky islands thick with stinging plants (maybe there is some kind of fruit-based filtering system within?). Needless to say, the sweet water is clogged with vast algal blooms and the sort of extraordinary insectile forms one might expect near-infinite sugar to attract. The sky over the second sea is a thick, luminous yellow, as if a ferocious sun were doing battle with an enormous cloud bank. It is an awful place. Those who have come back from it are generally not fond of cherries.
3. The water in this sea seems to become thicker as one ventures further in. It grinds together like ice, although the weather is only moderately cool. Sailing into it is incredibly perilous and should only be undertaken for short distances and with a reinforced hull. There are many tales of ships who have entered unknowingly and their unfortunate ends. Needless to say, a swimmer could not last long in the milling waters, half-transformed to stone. They say if you could get through the transition zone this sea would be walkable on, and maybe it does not count as a sea at that point, even if one can still over the centuries feel the movements of great stone whales below.
4. There is no light here; no sun or moon or stars and (as far as we know) no phosphorescent seaweeds of the like. One can bring one’s own light sources, of course, but so far none have shown anything but a black, brackish sea against a black sky. The longest a boat has stayed here and returned is an hour. Depth soundings have yet to reveal evidence of a sea bed.
5. There is a perpetual smell of peat on the air; much more than the occasional small islands could produce. This is perhaps the friendliest of the seven other seas and there are some travellers who claim to have stayed here for weeks with little ill-effect. It is still notable that maybe one in three of those who have been in fail to come out. Therefore there must be some hazard, even if we are unable to say what it is.
6. We do not know anyone who has been to the sixth sea. Some say that it was invented to make sure that there were seven other seas and not six. Alternatively the entrance may be very remote or very small, or its waters peculiarly hostile.
7. It is a shallow sea, and can be waded in in places. The sun shines very hot on its nearer parts, which are windless and smell strongly of the thick red seaweed that grows there. It is not known how far this sea stretches, though no-one has found an end of any sort other than a few lonely sandbanks. But one cannot sail here other than in tiny rowboats or punts, so it is hard to travel far. There have been explorers who were determined to prove that some miraculous feature existed, somewhere deep beyond the bland inner reaches of this sea. We waved them off, and we have not seen them since. I suppose if they found their utopia they might have stayed, and be still living.