I like ocean-themed projects, the ocean, and projects without a lot of complicated steps. Here is a beanie that is tough enough to be punk and subtle enough to show your love for the sea!
Unroll beanie, lay flat, prepare. (I got this anchor stencil for .59 at a craft store--I know the finished version looks huge, but this stencil is probably about 5-6 inches high).
Paint woodblock stencil, position lovingly on hat, press down. Hum one line of your favorite song (for funsies).
Pull off anchor, repeat step 2 if image isn't dark enough. Let dry overnight. Wear.