The tragic incident happened earlier this month at Masokut Island, a popular spot for surfers ... when a swordfish jumped out of the water and struck Manfrini in her chest.

Manfrini reportedly suffered a wound 2 inches deep ... and was taken to a nearby health clinic. Sadly, she did not survive.

"You surfed life and traveled the world doing what you loved most," one of her 22,000 Instagram followers said of her death in the comments.

"You left this as a lesson. Live enjoying life to the fullest and die doing what you love most. Hopefully, she didn't suffer much. Surfing the cloud. 💔"

Manfrini had a background in professional snowboarding before she fell in love with surfing. She also worked as an instructor ... and was the co-founder of AWAVE Travel.

Manfrini called herself a "surf frother" -- a person passionate about surfing -- and a pow (snow sports) addict.

Her death comes one month after surfer Jorge Alvarado hit his head while riding the waves at Daytona Beach Florida. He was 49.