A Mountain Dew advertisement that has premiered ahead of the big game on Sunday has shocked viewers, who compared it to a horror film critics called "the stuff of nightmares".

The video features four-time winner Seal Henry Olusegun Olumide Adeola Samuel in the most terrifying way possible.

The British singer's face was generated onto the body of an animated seal, which then proceeds to sing a jingle about drinking Mountain Dew.

At the start of the ad, American singer is standing in her kitchen innocuously checking her phone when she is offered a bottle of Mountain Dew Baja Blast.

She takes a sip and is instantly transported into a speedboat for a ride around a lush landscape.

But the expression on her face turns into one of panic when she sees the singer as a seal hybrid perched on a rock, serenading her about the joys of drinking Mountain Dew.

Seal modifies the lyrics to his hit single Kiss from a Rose, instead belting: "Baby, I compare it to a kiss from a lime, on the bay."

Horrified viewers have taken to social media to comment on the advert, with one pointing out: "The Seal Superbowl ad reminds me soooo much of Tusk. It's terrifying and I hate it!"

Tusk is a body horror film starring Lily Rose and Johnny Depp that came out in 2014. It revolves around the terrible experience of a podcaster who flies to Canada to interview an internet sensation, only to end up wandering right into the trap of a serial killer.

Wallace Bryton (Justin Long) is then mutilated and stitched into a walrus suit, in scenes that a critic has described as "gruesome" and "haunting".

Michael Pementel added: "The combination of all that human flesh along with Wallace's eyes staring out is enough to send chills down one's spine".

Meanwhile, another viewer complained: "Seal's head on an actual seal is not sitting well with me. Nightmare fuel."

However, a third commended producers for catching the attention of audience members, saying: " 'Hi Seal, this is Mountain Dew, can we turn you into an actual Seal for our Super Bowl ad?' Crazy ad, but we're talking about it..!"