Mermaid Problem/Playing With

Basic Trope: A male character starts a romance with a mermaid and can't figure out how to go all the way.
 * Straight: Bob the human meets Alice the mermaid - they fall in love but can't make love.
 * Exaggerated: Bob will vow to never have sex due to his love for Alice.
 * Justified: Alice the mermaid lays eggs.
 * Inverted: Alice the mermaid can not figure out how to make love to Bob the human.
 * Alternately, Alice is a "reverse mermaid" (fish above the waist, human below).
 * Or Alice is a human woman and Bob is a merman.
 * The same problem, but with a bird woman instead of a mermaid.
 * Subverted: "She has a mouth."
 * External fertilization.
 * Turn out that part of her scales, just below her waist, can split and reveal vital organ.
 * Double Subverted: Alice insanely bites down like a shark when he tries it.
 * Parodied: Bob is a "mersexuial" but has no idea how to make love with mermaids. It amuses mermaids to not tell him.
 * Deconstructed: Despite superficial similarities, mermaids and humans are far too biologically different for a romantic or sexual relationship to work. They have fundamental misconceptions about how such a relationship would work - Bob can't get past her lack of 'equipment', Alice doesn't understand why he sees sex as more than just reproduction. They have a short, rocky relationship and go their separate ways.
 * Reconstructed: Bob has a fetish for mermaids, and Alice has a fascination with humans. They make it work.
 * Zig Zagged: Bob and Alice the mermaid can't make love. Alice has herself turned into a human. Bob turns himself into a merman. Of course since she was a Mermaid until recently, Alice knows just what to do.
 * Averted: Alice is a human woman wearing a prosthetic tail over her legs.
 * Mermaids in this setting are aquatic mammals and possess fairly similar genitalia.
 * Bob and Alice don't want to have sex
 * Alice has two tails instead of one, with female genitalia in between.
 * Enforced: "We can't have love making on screen. Make Alice a mermaid."
 * Lampshaded: Bob: "I have to do WHAT?"
 * Invoked: Bob is trapped on a planet of incompatible mermaids as a form of Ironic Hell.
 * Defied: Bob has no problem working out the biology of her kind.
 * Discussed: Alice: "I'm ready Bob, take me now!" Bob: "How do I do that?" Alice: "Loser."
 * Conversed: Alice: "My boyfriend will not make love to me." Carol "He is a human. Did you ever tell him how?"
 * Played For Laughs: "I put it where?"
 * Played For Drama: Alice thinks because of this problem she and Bob were never meant to be.

Back to the Mermaid Problem - we think the answer may involve seamen.