Attached is a datasheet for a water level detector that works using two metal probes very close together . This can be made using
a cork with two small holes punched through it or some material that you poke the probes through and hot glue them to the material at the holes. They should be as close together as you can get without actually touching (1 to 3 mm).
Look at figure 3 & 4 on page 5 for example circuits. I have used this chip and it works well. There are a bunch of example circuits on those pages.
The DHT11 Sensor has a range up to 90% humidity.
LM1830.pdf (121 KB)
DHT11.pdf (842 KB)