Deep elves are born of the Arcfey's desperation for elves drowning at sea. Begging the Matron of Nature and the Harvest Bringer to save their creation, the tides forgave, fusing Green and Water magic.
Javarn Baldithas, The Elven Diaspora
Deep elves are the only kind of elf borne of the four Titanic Element, specifically the element of change, Water. The myth has it that the frist deep elf was the Wave himself, and countless others in the first generation were created the same way. A deep elf doesn't stray far from their reef, but you can find their countless reefs dotting the oceans of the world.
Finding a deep elf above land isn't a necessarily uncommon sight, though it would be finding them far from a major source of water. You'll often find a deep elf enclave in any major port city or even a fishing village, but you're hard fought to find one in a massive desert far from any river, lake, or ocean.
The wode and high elves on the surface have their flourishing wodes of Green magic, and the shadow elves of the Dark Maze have their decayed wodes of Green and Rot magic. The deep elves of the world's seas have their own version of a wode, known simply as a reef.
These reefs are exactly as described by their name, flourishing areas of vibrant coral and colourful algae. And much like their wode counterpart, the homes of deep elves are fused with the natural flora and fauna of the depths.