I've always been fascinated by the part in Ursula's spell when she summons the winds of the Caspian Sea ("come winds of the Caspian Sea!") and have often speculated about what it means within the world of the Little Mermaid.
If you look at a map, you will see the Caspian Sea is an exorbitantly large lake in Western Asia. While it is not connected to any of the other seas or oceans, and its water is a lot less saline, it has throughout history usually been called an "Inland Sea". In fact, it is one of the famous Seven Seas from antiquity. It is populated by a wide variety of fish, and even has a population of seal! (the Capsian seal) And from what I could gather, there are also legends of mermaid/merman-like beings in the region. But interestingly, there's, for example, no sharks living there.
Now the important part to take away here is that, it's a lake/inland sea...meaning it is not connected to the other seas and oceans. And unlike humans who can sail to islands, the merfolk have literally no way of getting to the Caspian Sea. There was historically no river or anything that connected the CS to the ocean.
Of course it's possible that the Merfolk of the oceans have learned about it from seabirds (with whom they can communicate)...or even perhaps from humans (because there has to be contact between merfolk and humans sometimes)
Or...and this is what I personally would find the most interesting...What if most merfolk don't even really know about it? What if, to them, it's just some mythical place or otherworld, like (for example)Tir Nan Og for humans?
What if for most ocean dwellers it's just a legend and a story, and only those who are very skilled in lore and magic know about it. This, to me would explain why Ursula is calling on the winds of that sea for her spell. It's a "magic place" often referenced in magic spells and books.
What do others think? Has anybody else ever wondered about Urusla mentioning the Caspian Sea?