“You just feel the tentacles, the suction-y things — I don’t know the right term — but I could feel it, and it hurt,” he said.

It was, he said, a “moment of yuck.”

The moment of yuck, now the subject of a viral Instagram post and international news media attention, was captured by Taiyo Masuda, 23, of Sydney, Australia. Both men are paid ambassadors for GoPro, the camera company, which could not have planned better exposure for the release on Thursday of its new Hero 7 model.

Mr. Masuda said in an interview they were among a group of about 10 kayakers watching a group of seals relaxing on nearby rocks. When one seal began swimming near the group, he got his camera out, hoping to get some underwater footage.

Then: smack.

“We instantly laughed so hard,” he said, before quickly adding, “Kyle was a little more pained.”