Shawn Mendes Takes Bathroom Break on Malibu Stroll With Bruna Marquezine

Shawn Mendes and his girlfriend Bruna Marquezine looked like they were enjoying a laid-back day in Malibu ... though things got a little too casual at one point.

TMZ has obtained video of the "In My Blood" singer out for a stroll with the Brazilian actress when nature suddenly called.

In the photos, Shawn is seen stepping off to the side of the road and turning the spot into a makeshift bathroom while Bruna hangs nearby.

Bruna doesn't appear bothered by the impromptu pit stop ... in fact, she's seen giggling during the moment, clearly finding the situation amusing as Shawn handled his business.

That being said, the pair seemed really relaxed during their seaside walk. They were also spotted chatting and enjoying the sunny Malibu weather.