It’s true: Aquaman has huge physiological problems. The temperature, the osmotic gradient, the pressure would all kill him, he’d never be able to maintain the caloric intake needed for his super-swimming ability, and the psychic screams from all those fish would drive him mad. But Southern Fried Scientist missed one, and this is the one that always ruined my childhood fantasies of growing up to be Aquaman: oxygen. The dissolved oxygen in seawater is much lower in concentration than in the atmosphere, so all that activity has to be carried out by an oxygen-starved brain and musculature. If Aquaman had gills, they were tiny and discrete, hardly adequate for the job; if he was using the respiratory surface of his lungs to extract oxygen, well, tidal breathing is incredibly inefficient, and using the delicate membranes of the alveoli to generate negative pressure in a dense medium like water, they were going to be shredded. Aquaman dies, twisted by osmotic shock, brain numbed by oxygen starvation, with a cloud of blood gushing out of his mouth.
I really did used to like Aquaman, and he was one of my favorite superheroes, just because I loved the idea of being able to dive off a dock and swim forever. But when I started thinking about it, on every page my brain would be shrieking, “HOW ARE YOU RESPIRING, AQUAMAN?” and I’d be distracted.
Lesson learned: less thinking.