Q.How to transfer a trailing pothos plant that is partially in water?
I have a pothos plant that is planted in soil with a trailing vine that has grown about 5 long (10-14 in) roots into the water of my fishtank which span 7-in of the vine. The vine continues past the fishtank, wrapping around a shelf for another 14-in and only has aerial roots (not in water) on this portion. I am curious if this vine would die if I were to take the roots from the fishtank? I ask because I would like to move the plant to a new location to better display. I have read that pothos do not do well when transferred from water to soil but am not sure if this applies considering the base of the plant is in soil. (These numbers are estimates)

Remove this vine from the water and cut into 'sections' for cuttings. You can continue to grow the roots in water or if the roots are long enough you can go ahead and pot them up.
https://www.gardeningknowhow.com/houseplants/pothos/propagating-pothos.htm
This would be a good time to prune up and clean up your original plant. Keeping it cut back will give you a bushier and less leggy plant.
These articles will help you.
https://www.gardeningknowhow.com/houseplants/pothos/propagating-pothos.htm
https://www.gardeningknowhow.com/houseplants/philodendron/pruning-philodendron-plants.htm