first of all what do you mean book the dark cave tour? you literally pay for the ticket at the ticket station lol
do not try to do guided tours as you don’t really need it. save your money and just do it on your own.
read about latest price of dark cave here.
I mean there is just one cost which includes the entrance fee, mud bath, zipline, kayak. its 450k vnd.
very muddy and wet hehe. see the pic below.
yes there is a changing room and you get a locker where you can put your dry clothes and phone.
Yes can bring your camera to the dark cave but you have to use a waterproof camera with a wrist strap. They won’t allow you to bring the camera without a wrist strap, super important!
mud bath is hella fun man. its the shower after the bath which takes quite a while to remove it all.
for the phone, just put it in locker as i said above
dark cave is open 7:30 am till 4pm if my memory serves me right. and for the tour it would take you around 2 hours to do all activities of mud bath, kayak, swim, zipline
just go, I am like 99% sure you will have fun there 