A euphemism for cunnilingus, eating pussy; also referred to as "going down," or "diving under the labial waves." In certain, traditionally conservative communities, this activity is frowned upon and reference is frequently found on signs near lakes and rivers announcing "underwater swimming is prohibited." In recent years, a fad similar to planking has emerged among college-age youth, whereby photographs are taken of couples engaged in "underwater swimming" with the signs stating the prohibition of such activity appearing in the background; this has come to be known as "stanking."
Shawna's bulging little camel toe was more than I could take, so I pushed her back onto the hood of the car and ripped her panties off. Then I took her underwater swimming until we were both drenched and well satisfied.
Everett really surprised me and totally proved the myth isn't true. After we made out for a while, he went underwater swimming and didn't come up until my toes curled!