This quote right here though. Smdh...
Q10: Does the vagina of a dolphin always contract after penetration?
A10: Yes, for the most part, but sometimes they like to let you do all the work. That goes for pleasuring as well as mating. I was reminded by another zoo that if a female doesn't want to participate, they can contract their vaginal muscles tight enough that nothing could penetrate them. The other zoo also pointed out, that a female can do a lot more than just contract their vaginal muscles. By expanding their upper vaginal muscles they can emulate sucking and blowing. They can also ripple the muscles vaginal canal both upwards and downwards, in a milking motion.