The first time I went scuba diving, I saw nothing but mud. The last time I was diving, I hovered just above the ocean floor as hungry sharks fed on our “chumsicle” — a frozen mass of fish designed to attract the finned creatures. Last fall, a friend of mine enrolled in Cornell’s Open Water Scuba gym class. After an Oscar-level performance of puppy-dog eyes and some well-timed Jaws jokes, I agreed to take the class alongside him. I was terrified; who breathes underwater for fun?