A pair of dolphins leap in the Atlantic Ocean, Jul. 18, 2013. Reuters

Scientists at Dalhousie University in Nova Scotia are looking to answer some tough questions—namely, what is dolphin sex like? Postdoctoral fellow Dana Orbach presented 3D scans of the reproductive systems of marine mammals at Sunday’s Experimental Biology Meeting in Chicago, showing just how complex and intriguing their sex lives are.

“Copulation is the most direct possible interaction between males and females,” Orbach told the journal Science in an interview Sunday. “But we know so little about it largely due to the physical challenges of studying it, especially with underwater creatures.”

Read: Sea Otters Show Intelligence Just Like Dolphins

Along with Sarah Mesnick, an ecologist at the Southwest Fisheries Science Center, Orbach published a study in March in the journal PLOS One detailing the intricacies of a variety of marine mammal vaginas. Orbach collected the reproductive tracts of some 75 marine mammals that had washed up on beaches of natural causes. She then proceeded to clean them, measure them and create a silicone mold of their interiors.

The final step: inflate the male mammal’s penis using a pressurized keg of saltwater and insert it into the vagina.

A pod of dolphins swim in in the sea in Kalpitiya, Sri Lanka, Feb. 12, 2017. Reuters

“The flaps, folds and blind alleys of the female reproductive tract may serve as a gauntlet that a male’s sperm, or that of competing male rivals, must traverse to reach the egg,” Mesnick told National Geographic. “All evidence so far seems to suggest that sexual selection seems to be driving this variation. It’s a pretty amazing system to be working with.”

And there’s a possibility some dolphins might just be having sex for fun, something the study’s authors intend to find out.

“They have sex all year round even when they can only conceive for certain periods of the year,” Orbach told Science. “By looking at how the genitals align, we can now say certain body positions are more likely to lead to successful fertilization than others, which might be for purposes other than reproducing. Is it play? Is it working out hierarchies? Is it establishing dominance? Is it learning? There could be many functions of sex.”

The researchers said they hoped the study might provide information that will prove vital to the conservation of dolphins and other marine mammals by assisting captive breeding in an attempt to increase endangered populations

“Across the animal kingdom, we can see and hear many aspects of mating, such as bright colors of courting males – or their songs – and the ensuing courtship rituals between the sexes,” said Mesnick. “But in species with internal fertilization, there’s just as fascinating a scene that goes on beyond our ability to see it. What happens inside the female’s reproductive tract – the ultimate playing field for sexual selection – is just as important in influencing reproductive success.”

Dolphins swim at the zoo in Duisburg, Germany, Feb. 17, 2016. Reuters