http://forgottenrealms.wikia.com/wiki/Merfolk
For whatever reason, some of my viewers asked about Merpeople activities. Specifically sexual.
While I absolutely condone whatever depravity you conduct in the privacy of your self, I'm not sure what you expect of me here.
Here goes.
The mer people of Faerun have a simple saying regarding their mating rituals, "the more the merrier."
Merpeople are not rapists (like ducks: http://www.quora.com/Does-the-Cracked-article-on-duck-rape-have-any-validity). At least not on the whole; they're still racist, violent, and generally unpleasant if you're not naturally a water breather.
The mer people can be reasoned with, they can be treated and traded with, however these relationships do not develop easily or in short term. Mer people are naturally distrustful of surface dwellers for typically friendship is extended for their resources and any chance to take control of a mer person has demonstrated the sky borne to be insensitive and outright cruel to those under the sea.
So in short, while a mer person may drag you to your drowned doom, they are no more or less likely to commit an act of underwater sodomy upon you. Unlike a Dolphin. Which may attempt to rape and would subsequently kill you.
You're probably wondering how large a mer dong is and in short, they vary in size. I just rolled 2 d20s and we'll go with them given that mer people are medium humanoid sized. Minimum size is 5", maximum is 14". There are of course, still exceptions to the rule.
K,that's it. That's all I'm writing. Some of you have rights to edit and add to these wikis. Feel free :)