I weigh it a different way using the 0 ing feature on the scale
first I weigh the rock= 356
Then i put my water container on the scale and 0 it.
then i suspend the rock completely covered in the water not touching the bottom or sides= 108 : for smaller peices I use lighter string or fish line
devide the dry weight by the wet weight
356/108=3.296
this just takes the constant; weight of water and container, out of the picture