Echo explained a lot about mermaids to you. For example, there are no natural mermen, they only occur when someone gives a man a tail, as she had done to you earlier. She also started teaching you the basics of speaking under water. It was when she explained that most mermaids were lesbians, and touched one of your breasts, that human matters came to mind.
"Echo, I have a girlfriend."
She took her hands off you, "I think you mean you had a girlfriend, Ariel. Back when you were a man, not a mermaid."
"It's not that I want you to stop-"
"Good," Echo said. She swam around you and then hugged you. The feeling as your breasts touched almost made you forget what you were saying.
"It's just that I don't want to leave her hanging. I have to say goodbye."
Echo let go of you and swam a few feet away, then she turned back and looked at you in annoyance. "So you've been a mermaid for a couple of hours, and you want to go back on land?"
You shook your head, "Of course not," you didn't want to give up your tail for even a second. "She lives by the beach." In fact she seemed to like the sea just as much as you, if not more. That gave you an idea, "If she wants to, could you change her into a mermaid too?"
Echo considered the idea, and then asked, "Will she share?"
You answered her honestly, "I don't know."
"Ok, lets do this thing, but afterwards we get to have some fun, right?"
You smiled -no- you grinned, "Right."
Echo led you to the shore, and from there you led the way to your girlfriend's house. It was harder than you thought it would be, everything looked different from the water, but by early evening you found yourself at the beach in front of her house.
"Ok, so we're here. Now what?" Echo asked.
"We need to get her attention. Can you do something?"
"I can give you legs so you can walk up to-"
"No! The tail stays. It stays forever." Echo seemed to enjoy that response, in fact she beamed. "I guess we'll just have to find a way to get her attention from here." You didn't think shouting would work, so after some thinking you started picking up small pebbles. Once you had several you started throwing them towards your girlfriend's window. Echo proved to be a better thrower than you and soon your girlfriend, Cassandra, came outside to investigate.
You called to her and she came down to the water. When she got there she asked, "Who are you, and why couldn't you just come up to the house?"
"Because I'm a mermaid," you said as you lifted your tail out of the water and bent it in a way knees would never allow. For a moment Cassy stood silently and wide eyed. Then she asked to touch your tail. When you said she could she ran into the water, not even bothering to take her shoes off, and started stroking it. The feeling was wonderful.
After touching every part of your tail, Cassy turned to look at you face to face, "Ok, you're a mermaid. Your tail isn't just real, it's the coolest thing I've ever seen. Why are you here?" she asked. She added, "Not that I'm not grateful," after a beat.
"I know that you're going to have trouble believing what I'm about to tell you, but remember: I'm a mermaid. That probably seemed impossible before you saw me here," you started, and then launched into telling her that that morning you had been her boyfriend, and everything that had happened since. You introduced Echo along the way, and told Cassandra that you'd renamed yourself Ariel. You had to tell her about things only the two of you knew to convince her, but in the end you did convince her. "I don't ever want to go back to being human, or to being male. I've got a new body, a new name, and I'm going to start a new life in the ocean. I just didn't want to leave without saying goodbye ... or offering you a chance to come with me."
Cassandra backed up a step, "What?"
"Echo will change you into a mermaid, if you want," you told her.
"If you share," Echo added. "You can't keep Ariel all to yourself."
You watched as Cassandra considered it, her clothes were soaking wet and you could tell she was cold. You wondered what she was thinking. It was a strange position to be in, standing fully clothed in the ocean in the evening, with two mermaids in front of her, one of whom used to be her boyfriend, being asked to decide whether to become one herself.
You found that you didn't care what choice she made, as long as it made her happy.