There are a few ways, as long as you carried around something to immerse yourself in
Firstly, you would need to carry around a box/bathtub/container/coffin large enough for you to immerse yourself in. When taking a short of long rest you can then fill it up with some of the below options:
Using the Decanter of Endless Water you could fill it with water most likely using the Stream or Fountain options:
- "Stream" produces 1 gallon of water.
- "Fountain" produces 5 gallons of water.
How you acquire the Decanter is another question though, so you would need to ask your DM if you could reasonably have found/purchased one ahead of time. Since that the campaign apparently starts characters off at level 1, it may be a hard sell.
As Miniman mentioned you could also use Create or Destroy Water which is a 1st level spell available to Clerics and Druids. You can use it to:
Create up to 10 gallons of clean water within range in an open container.