Venturing into mixed martial arts’ treacherous waters for the first time in her career, Claressa Shields knew she would be swept under. The adjustment to grappling, leg kicks, submission techniques and cage awareness has proven difficult for some of the most accomplished boxers.

But after Shields fought to stay afloat against Brittney Elkin throughout most of her MMA debut in the Professional Fighters League on Thursday night, she found buoyancy, and eventually, victory.

After struggling to mount an assault against Elkin (3-7) through two rounds, Shields (1-0) turned the tide against the veteran grappler in the third, pummeling her opponent to earn an impressive stoppage victory as she begins her journey to conquer women’s boxing and MMA simultaneously.

“I feel like I am dreaming. This is crazy,” Shields said after the fight.

“I kept telling myself, ‘It’s going to be hard,’ because it’s a whole different world. I’m like, ‘It’s going to be hard,' and 'Do not expect an easy win.’ Every time I sat down in the corner I said, ‘Dang, I lost another round.’ ... When I tell you that third round came, I said, ‘I’m bout to just dog her.’ And I went crazy after that. I am not losing.”

Predictably, Elkin, a Brazilian jiu jitsu brown belt, relied on her grappling to smother Shields in the first two rounds, limiting Shields’s offense, but the novice mixed martial artist showed flashes of solid takedown defense.

Late in the second round, Elkin’s ground work seemingly set up Shields’s demise when, with 20 seconds remaining, she tugged on Shields’s left wrist to execute an arm bar. But Shields wriggled free and spent the last 10 seconds punishing Elkin’s with hammer fists.

Elkin dragged herself upright after the bell. Shields, who seemingly suffered little damage throughout the fight despite her compromised position, gained confidence.

“I’ve been doing MMA for seven months, she’s been doing it for 12 years, so I knew I was at a disadvantage. But I also knew too that I’m just a different kind of animal. Even though I felt like I was losing, I still felt like, ‘We still have time.’ ”

Shields landed two powerful right jabs in the opening seconds of the third round before Elkin attempted another takedown. Her coaches had demanded she not succumb to a third-round takedown and she listened, sinking her hips and sprawling her legs to loosen Elkin’s hook around her left thigh.

Shields escaped to her feet. Her coaches told her to let Elkin up, to rely on her strengths and fight standing up. She refused.

“I was like, ‘For what?’ No,” she said. “I had her where I knew I could just take her, just give it to her. She wasn’t strong enough to get me up so I just kept hitting her, kept hitting her and I told myself keep hitting her until she quit."

Shields stunned Elkin with a left hook from above. Elkin rolled to her side and Shields pounced, pounding Elkin for more than a minute before referee Gasper Oliver called the fight at 1:44.

An exuberant Shields, now undefeated in both of her professional careers, rose and screamed. Her mother, using a black cane with her right hand, raised her left in triumph. Shields found her from inside the cage and shouted.

“Mama. Your daughter a dog," she said. “Your daughter a dog. C’mon!”

Review the rest of Thursday night’s card below.