Taking a double dose of Ex-lax after eating Mexican food and waiting until it's unbearable, then punching your girlfriend in the diaphragm, knocking the wind out of her. While she's lying on the floor sucking for air like a fish, unleash the liquidous mess from your anus into her waiting mouth.
Other fish can be used to relate to the person sucking shit matter.
EX) Rainbow Trout for lesbians, Wide Mouth Bass for that annoying chick who won't shut up, etc.
Nick: My girlfriend told everyone my dick was like a pencil with broken lead, so last night we went to On the Border and then I gave her a Whitebass Choco Splash.