I think it was more shock than drowning. He hadn't swallowed much water. Maybe he was stung while diving.
5 seconds sound clip from the The Treasure of the Sierra Madre movie soundboard.
You can hear this line at 01:25:44.857 in the Blu-ray version of the movie.
Quote context
[...]
- Look after my goods while I'm gone, huh?
- Tequila.
- Artificial respiration did it and a few boy scout tricks.
- What gets me is how these Indians knew we were in this neck of the woods, anyhow.
- When you're near their villages, they always know. Don't ask me how. They just know.
- ¿Por que se Van de la comarca?
- Tenemos negocios importantes en durango.
- No se vayan tan pronto. Queremos que esten con nosotros una semana.
- Muchas gracias por la invitacion, pero necesitamos estar en durango en dos semanas.
[...]