"Some half-elves in Faerûn have a racial trait in place of the Skill Versatility trait. If your DM allows it, your half-elf character can forgo Skill Versatility and instead take the elf trait Keen Senses or a trait based on your elf parentage."
When you make a half-elf, just normal, you don't get the option to take keen senses. If you may, say, an aquatic half-elf, you only get the swimming speed with no option to instead stick with skill versatility or keen senses.
You forgo skill versatility for the elf parentage trait. You wouldn't be able to have an aquatic half-elf with skill versatility. You are either a half-elf with skill versatility, or you are a different variant of half-elf without skill versatility and instead some other feature.
Jeremy Crawford commented that the keen senses is superfluous. Basically, ignore it to take one of the elf parentages. Since skill versatility gives you two proficiencies and keen senses only gives you proficiency in perception it is unnecessary. You can just take perception as one of the skills for skill versatility.
"Some half-elves in Faerûn have a racial trait in place of the Skill Versatility trait. If your DM allows it, your half-elf character can forgo Skill Versatility and instead take the elf trait Keen Senses or a trait based on your elf parentage."
When you make a half-elf, just normal, you don't get the option to take keen senses. If you may, say, an aquatic half-elf, you only get the swimming speed with no option to instead stick with skill versatility or keen senses.
You forgo skill versatility for the elf parentage trait. You wouldn't be able to have an aquatic half-elf with skill versatility. You are either a half-elf with skill versatility, or you are a different variant of half-elf without skill versatility and instead some other feature.
Jeremy Crawford commented that the keen senses is superfluous. Basically, ignore it to take one of the elf parentages. Since skill versatility gives you two proficiencies and keen senses only gives you proficiency in perception it is unnecessary. You can just take perception as one of the skills for skill versatility.
https://twitter.com/JeremyECrawford/status/664308174560690176