In English, the title of this movie is "Danger in the Abyss." It's an Italian fake documentary, famour for its great jazzy soundtrack. The soundtrack album is prized by collectors of unusual music. The movie is basically just an excuse to show sexy women in bathing suits getting attacked by dangerous animals. (It reminds me of the similarly misogynistic bloody low budget Italian "Giallo" horror films made in the same era in which beautiful women were stabbed and slashed to death for our entertainment. Come to think of it, that pretty well describes a lot of thrillers.)
In the snake scene, we first see a black sea snake swimming, then two women wearing bikinis and snorkels swimming underwater. After a short time, we see what is supposed to be a sea snake pestering the divers. (For the scenes with the divers, they used an eel, not a snake, to portray a deadly sea snake. Sea snakes are flattened only at the tail, this creature is flatten throughout the body.) Then the snake (eel) starts to pester the women, eventually biting both of them on their bathing suits. (I suspect that the eel was lured to that part of the diver's body by some type of food placed in their suits.) The women both convulse and die, but not before one of them takes off her bikini top to show the bloody bite mark on her breast. Finally we see a real sea snake swimming to the surface for air.
You can watch this scene on YouTube.