Also, the argument that Ariel could have written to Eric is...well...

"Dear Eric, hi, I am a mermaid who gave up her voice to an evil sea witch to turn human, I have 3 days to get you to kiss me."

Eric: gotta go -Naruto runs outta there-

Not likely. Eric would have been spooked, I think.

Why not, I think he actually believed in mermaids/merpeople. He was around sailors and they talked about stories of them, so maybe it wouldn't be so strange to him.

He thought she was the one he was looking for when he first saw her, almost immediately, the only thing that was missing was her voice, if she explained what happened I'm sure he would believe her. Like she could easily say "I was the one who was singing to you on the beach and rescued you from your ship wreck" that would instantly be something only the woman that saved him would know, and back up her story. The argument that she couldn't just write about it is the one that's a bit far fetched when she can clearly write her name, so why not other things?

I agree with disnerdtobe. And I think Eric would be inclined to believe her if she could write it down.

She'd end up getting locked in the looney bin!

Eh, Eric strikes me as the type of dude who trusts his gut and he was actually already hoping she was the same girl.