Corcovado: overnight Sirena & San Pedrillo

On August 1st, I have booked a two-day excursion in Corcovado National Park. We will be doing the "overnight Sirena-San Pedrillo tour."

I read that this is the more adventurous tour with long hikes: 16 km and 10 km.

I wonder how intense and adventurous this tour really is. And whether the tour is "safe."

I read that you need to bring water shoes, as you will be crossing rivers. How deep are these rivers? And is this safe?

I am also a bit worried since the fer-de-lance snake lives in the area. If we stray from the walking paths, there is a risk of stepping on this well-camouflaged snake.

In the event of an accident, does the park have antivenom available? And is there an evacuation plan in place? Considering the park is very remote.

Any experiences are welcome!!