Gaseous release after waking up from a night of bareback cum dumping. The fermented load may bubble or foam around the sphincter in accompaniment of said release.
Depending on the virility of the swimmers and the depth of their climb this can be experienced though out an entire day.
"Damn it bitch, load fart in my pants. You really gotta stop blowing in my ass"
"Ugh what is that rank, did you just blow a load fart?"