This is from 5 years ago on reddit. There's also a really wild copy pasta a bit like this on dolphins.
There are various ways a dolphin has of showing that she or he is interested in sex. Males are probably the easiest to detect. They will swim around, sporting an erection (anywhere between 10 to 14 inches long for a Bottle-nose), and will have no bones about swimming up to you and placing their member within reach of your hand. If you are in the water, they may rub it along any part of your body, or wrap it around your wrist or ankle. (Dolphin males have a prehensile penis. They can wrap it around objects, and carry them as such.) Their belly will also be pinkish in colour, which also denotes sexual excitement.
Females can be a little harder. The most obvious way a female dolphin has of displaying her sexual interest is the pink-belly effect. Their genitals become very pink and swollen, making the genital region very prominent. They may be restless, or they may be acting as normal. If you are out of the water, they may swim up to you and roll belly up, exposing themselves to you, coupled with pelvic thrusts. If you are in the water, they may press their genitals up against yours, nibble your fingers, nuzzle your crotch, or do pelvic thrusts against you.
Each dolphins way of expressing sexual readiness varies, so the longer you know the dolphin, the better you will detect when they are sexually active. When a male dolphin is interested in you, about the only thing you can do, if you are male, is to masturbate him. (Unfortunately, I cannot speak for the female of the human species... it seems women just don't like dolphins enough...) WARNING! You should NEVER let a male dolphin attempt anal sex with you. The Bottle-nose dolphin member is around 12 inches, very muscular, and the thrusting and the force of ejaculation (A male can cum as far as 14 feet) would cause serious internal injuries, resulting in peritonitus and possible death.
A male dolphin's member is roughly S-shaped, tapered at the end. If you are in the water with them, it is best to support the dolphin on his side, just under the water, with one hand, and handle him with the other.
Male dolphins, I find, tend to prefer the base of the penis to be gently massaged and squeezed, as well as gently rubbed along it's length. It feels very much like the rest of the dolphin (ie. smooth and rubbery to the touch, but firmer). It doesn't take long for the male to ejaculate, around 40 seconds to a minute, and this is usually accompanied by either shuddering just prior to ejaculating, and thrusting and tail-arching during ejaculation. The force of ejaculation can be powerful at times, so it is best to keep your face out of the line of fire, or keep his member underwater. You can attempt to lick and suck on the end of it while masturbating as well, but be warned, do not try to give full throat, and get the hell out of the way before he ejaculates! A male dolphin could snap your neck in an accidental thrust, and that would be the end of that relationship. Well, the females are again a little trickier. There are two courses of action with a female fin: Masturbation, or mating.
Masturbation: Female dolphins, once they show interest in you, can be supported in much the same way as the male, one hand under the fin, supporting her, the other doing the stimulating. The clitoris of the female is located at the top of the genital slit, and is a prominent lump when erect. You can rub this with your finger tips, or lick and suck it, but with the oral aspect, you might end up with a bruised nose as they thrust up into you. You can slide your hand gently into their genital opening, and feel around inside, rubbing gently. They feel warm and muscular inside, their labia like tough, squishy sponge when they are excited.
Don't be surprised if they start to play with your hand inside them. They have very manipulative muscles, and can use them to carry and manipulate objects, including your hand. (They can do things that would make a regular human woman turn green with envy.) Their climax is coupled with stiffening, shuddering, sometimes a lot of thrusting, clinching of the vaginal muscles, and sometimes vocalisation. Mating: This is harder. Obviously, being human, it is awkward, but not impossible to mate in open water. It is easier to have the dolphin in a shallow area (like the shallows just off the beach) around 1 1/2 to 2 feet deep. This is usually comfortable enough for both the dolphin and you. Gently, you should roll the dolphin on her side, so she is lying belly-towards you. You can prop yourself up on an elbow, and lie belly to belly against her. You may want to use the other arm to gently hold her close, and place the tip of your member against her genital slit. She will, if interested, arch her body up against you, taking you inside her body.
There is usually a fair bit of wriggling and shifting, usually to get comfortable, both outside and inside. Once comfortable, though, females initiate a series of muscular vaginal contractions that rub the entire length of your member. They may also thrust rhythmically against you, so enjoy the experience while you can, since you will rarely last longer that a minute or two. Just prior to her climaxing, she will up the speed of her contractions and thrusts. It is interesting to note that the times I have mated with females, thay have timed their orgasm to mine. Whether they do this consciously or not, I do not know, but it is a great feeling to have two bodies shuddering against each other at the one time. One thing to note. Whether you masturbate or mate a dolphin, male or female, always spend time with them afterwards. Cuddle them, rub them, talk to them and most importantly, and show them you love them. This is essential, as it helps to strengthen the bond between you. Like a way of saying that this wasn't just a one night fling. The dolphins appreciate it, and they will want your company more the next time you visit them.
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