My French is really rusty, especially when it comes to understanding spoken French, so I can’t give you a word-for-word translation for most of it, but I’ll give it my best shot. If someone who speaks better French comes along and says I got stuff wrong, definitely take their word over mine. 
Opening text: The triton is a sea god, son of Poseidon and Amphitrite, the messenger of the waves. Legend says that tritons are the masculine equivalent of sirens. They have the power to unleash passions to the rhythm of the ocean waves. They can live on land, but sadly, upon leaving the depths of the sea, little by little, they begin to lose their powers and even the memory of who they are. They cannot retrieve them except by coming into contact with another of their kind.
In the first scene, the boss is basically just organizing his lifeguards, telling them there’ll be a lot of tourists and then telling them where they’ll be monitoring today. Then I think he said something about meeting back there in 2 hours.
When the boss is talking to the triton, he just says “Hey, young man, this isn’t a tourist beach!” and then from context, I think he says “You have to leave”, but I didn’t understand the main verb. After they have sex:
- Triton: What’s the name of the lifeguard you were supposed to meet up with?
- Boss: It’s Mathieu (= Matthew).
- Triton: Where can I find him?
- Boss: That’s him over there, on the boat.
I missed a lot of the stuff with the lifeguards rescuing the drowning guy, but the gist of it is that the drowning guy is a journalist who was investigating tritons when he fell out of his boat. The lifeguard who stayed with him, on hearing about tritons, says “No, that’s us.” (not literally, just meaning that they, the lifeguards, are hot and horny). When the third guy asks how they’re doing, the lifeguard replies “I’m giving mouth-to-mouth. You wanna help?” I didn’t understand most of what they said after that, but it’s mostly sex anyway.
Red-bathing-suit guy says “Shit, I forgot my Walkie-Talkie.” Not sure what he says after that, but maybe something about rejoining the others? He then finds the boss and says “Hey, is everything okay?”, to which the boss replies. “I’m not sure. I’m not sure what happened.” Once they’re against the rock, the boss says something about the other guy being cute and then they start kissing. After they’re done, the guy asks the boss what happened to him, and the boss talks about meeting the young guy and how he had such a melodious voice. He’s confused, but then he remembers that the young guy wanted to talk to Matt. The boss suggests calling him on the cell phone, but Matt doesn’t answer, and they wonder what’s going to happen to him
The closing scene I couldn’t make out, but I think it’s something like “You’re so hot, my love.” and then the other guy maybe says something like “I’m glad I found you.”