I completed the waterfall quest o train on the fire giants but now i cannot et back into there. i just get washed down the waterfall. Do i have to get the amulet again?

Ya you have to use the pebble to get back into the grave to get the amulet again. I recommend just picking up a couple once you're there, just incase.

Thanks :)!

You will also need Pebble for Roving Elves quest , so you might wanna keep it . The amulet is good for returning to the cave to train on fires or for slayer tasks.