Why Is It…That many games seem to differentiate between so many types of Elves? We now have Sea Elves, High Elves, Aquatic Elves, Dark Elves, Wood Elves, Desert Elves, Tundra Elves, and plenty of others as well. It becomes predictable–an Elf that dwells in the Jungle, one that dwells in the Badlands. One that lives by Rivers, one that lives by Trash Heaps.
This is something that I’ve never really cared for, especially after it really started to get crazy around the time that Unearthed Arcana was published.
In my games, elves are elves. Even drow, though I’m not sure if I’ve ever actually used a drow in a game.
I would use a sea elf “merelf” just like I’d use a merman, though. That is really something different.
I can imagine some “monster” elves, as in encountered by PCs, as having special/different mechanics. Maybe some special tribe of elves all have outdoor tracking skills like a ranger or 10% magic resistance or whatever. But that’s no different than saying that native tribesman humans have +1 on all saving throws due to general toughness or that this clan of hobgoblins gets a +1 to damage due to great strength. I wouldn’t create new full-blown races and would not offer them as options for player characters unless it served a specific campaign.
Finally, I’ll admit that I spent some time pondering two elf races for our homebrew game, green elves and blue elves. But I ditched the whole idea after a little thought. I didn’t see a good enough reason for it.