I stood with my geology regional field class on a dark basaltic coast near Honolulu. I squinted my eyes, shielding them from the bright glare off the Pacific Ocean.

We were standing around a tall outcrop; the top of it was many feet above my head. When I inspected it closely, I could see fossilized coral that was trapped in time, frozen–it was an ancient coral reef.

The professor from University of Hawaii, Chip, was guiding us around Honolulu, and he asked, “If this is a coral reef, what does that mean about sea level?”

I would have been underwater when that coral reef was alive. I remember feeling strange. I was surrounded by air and cries of seagulls and kids.

I pictured all of this underwater. Deep sapphire blues enveloped me. When I looked up, colors faded to indigo to aquamarine where the surface of the ocean met the sunlight. Tiny schools of fish darted everywhere. Beyond the reef, the waters blended into midnight blue that turned black, hiding whatever lurked in the shadows.

I knew about sea level rise and climate change  before this trip, but standing there on the shores of Hawaii that were submerged gave me a new perspective.

The oceans are starting to rise. Shorelines are creeping closer and closer inland because ice sheets are melting faster than glaciologists originally thought they would in a warming atmosphere. Sea level rise is estimated between 3 feet to 16 feet or greater.

Where I was standing could really, truly be underwater again.