Step 1: fill up the tub just enough so your nob is out of the water.
Step 2: catch a fly and rip his wings off.
Step 3: stick the fly on the end of your prick.
Flies don't like water so he will just walk around the tip of your dick
Go home tonight and Trap one off. I did it this weekend. Felt amazing. Yet another thing to cross off the bucket list.