Brooks Nader and Livvy Dunne are turning up the heat on the "Baywatch" reboot ... because the first teaser is packed with barely-there red swimsuits, struts, and enough beach body eye candy to make Pamela Anderson proud.

The first footage dropped Saturday ... showing Brooks owning the dock in the franchise's iconic red one-piece while Livvy suits up for her acting debut in matching lifeguard gear.

Stephen Amell also gets his full "Baywatch" fantasy sequence ... sprinting shirtless across the sand with a rescue buoy in hand.

Fans immediately flooded the comments hyping up the reboot and the new cast, which includes Shay Mitchell, Noah Beck, and Hassie Harrison alongside Brooks and Livvy.

TMZ broke the story ... there's already competition brewing behind the scenes between Brooks and Livvy over who's becoming the reboot's breakout bombshell ... aka the next Pam Anderson. Our sources told us the next Pam chatter became a recurring topic during filming.

The reboot is premiering in January, with OG "Baywatch" stars Erika Eleniak and David Chokachi also returning.