Fins are a fun tool to mix up your pool workouts and work on your leg speed and/or strength. To be honest, they make kick sets fun and add diversity.

Streamline kicks-These can be done on your back or your front. Extend both arms above your head so that your in streamline position. The reason this position is helpful is that it helps engage your hips and torso. Many people often ask how do I make my kick stronger? You need to keep your legs straight, no bend in the knee, and kick from the hips!
Underwater kicks- go underwater and get into a streamline position. Give yourself a goal of a certain number of kicks, then see if you can add on as time goes by! This is a challenging exercise! But the point is to get a good number of kicks in, not to continually deplete your body of oxygen!
Change up your stroke- butterfly, backstroke, and breastroke are all great ways to change up your stroke and at the same time keep kicking. I fully agree that kicking can be tedious, but if you change up the strokes it makes it a little less daunting.
Sprinting- Use quick kicks. If you wanna go fast you gotta practice going fast! If you wanna be fast do quick knicks with fins. Then eventually lose the fins.
Treading water can be a huge challenge! It can also be a great skill to have on tap! Your head needs to to be above water, but the rest is very open to different options. Keep moving for a set time, keep at it and it will get easier with practice!!!!