We surfaced to sunshine, which lasted about as long as a polite chuckle at a bad pun. The trail from the water to the car climbs 150 feet—with terrain best described as “character building” by the understaters among us. Heather’s rebreather weighed in at 120 pounds—more than she does by a margin you’d notice on a seesaw. Her progress was slow and deliberate: step… pause… sigh… repeat. She made full use of the halfway bench, succumbing to that special brand of post-dive gravity that feels like someone added an exponent to Newton’s gravitational equation.

Just as we reached the car, it started raining—because of course it did. If you’ve never tried peeling off a drysuit in a downpour under the tailgate of a Subaru the size of a glove compartment, I highly recommend it as a team-building exercise. After some grumbling and tactical towel maneuvers, the rain passed, and we decided, in a move of questionable judgment, to hike up Gold Rock to see if we could spot the wreck from above.

Gold Rock, for the uninitiated, is a scenic bluff with no guardrails and spectacular views of Split Rock Lighthouse. Also present: a pair of highly protective peregrine falcon parents who did not appreciate our presence and conveyed this with shrieking clarity. We took the hint.

On the way home, I treated myself to a Blizzard from Dairy Queen—a full pint of dairy-based self-respect. It was my first meal of the day, which made it either breakfast or, given that it was nearly 3 in the afternoon, “linner”. Still hadn’t told Heather it was my birthday. There’s something lovely about holding a secret like that all day. Like carrying a cupcake in your pocket no one knows about.

Back at Heather’s place, we moved on to a small experiment—something we’d been pondering for weeks, and which, had we explained it to a responsible adult, would likely have been vetoed immediately.

You see, in the niche world of rebreather diving, the two most reliable ways to shuffle off this mortal coil are hypoxia (not enough oxygen) and hypercapnia (too much carbon dioxide). Both are as friendly as a bear trap in a bounce house. But a recent study by Dr. Simon Mitchell suggested that first-hand training in these unpleasant states might help divers recognize the signs before things get out of control underwater.

So there we were: two divers, two oversized dogs, and one profoundly questionable idea. We sat on Heather’s deck, rebreathers humming away, dog drool glistening on our feet. And then, as if auditioning for a Darwin Award, we turned off the oxygen. Don’t try this at home. Or anywhere, really.

Heather’s oxygen levels looked fine—right up until they didn’t. When her blood O₂ slipped into the 80s, I asked her what 9 times 4 was. She blinked. Nothing. Which was troubling, since she once minored in math and can usually multiply things without audible gears grinding. A minute later, her O₂ saturation was in the 70s, and I told her to come off the rebreather loop. Within half a minute, she was back to a perky 97%, no harm done. But here’s the unsettling part: she felt absolutely fine. Not dizzy, not short of breath—just completely incapable of basic arithmetic. In her head, she later confessed, she was thinking, “9 x 6… that’s 30-something,” and suddenly realized something was very, very off.

Hypercapnia was up next in our cavalcade of bad ideas. We removed the scrubber—basically the thing that keeps you from breathing in your body’s exhaust fumes—and breathed from the loop. At first: nothing. Then a slow build of weirdness. Tingling cheeks, slightly panicked lungs, and a vague suspicion that your body is quietly filing a formal complaint. It wasn’t a full-blown emergency, but it definitely felt like I was edging into “sweaty and confused at a parent-teacher conference” territory. The dangerous bit is how easy it would be to misinterpret underwater. You’d think, “Boy, these fins are heavy,” or, “Maybe I’m getting a cold,” right before you start breathing like a freight train.

We didn’t stretch it out—just long enough to learn what trouble might feel like before it actually became, you know, trouble. Hypoxia was sneakier than expected, like a ninja in socks. Hypercapnia came on more like a moody teenager: quiet at first, then suddenly slamming doors. It was all valuable, slightly unsettling knowledge. We learned a lot. But then I checked the time and remembered I had a pressing engagement—with a rack of ribs, a birthday cake, and the family who thinks I’m charmingly eccentric rather than mildly unhinged. I threw my gear in the car and made haste. Some science just has to wait until after dessert.

The evening was perfect. Grace had just moved back to Boulder, so it was just Shari, Isabel, and me. (🙁) We hit OMC for a BBQ bonanza. I had cocktails, brisket, ribs, biscuits, fries, creamed corn, and possibly a small coma. At home, Isabel presented a cake that might one day be ruled illegal in several states: chocolate, Oreo, and peanut butter. It was magnificent. I ate a week’s worth of calories and didn’t regret a single molecule.

The next day, I had an apple and a PB&J—and felt stuffed.

The rest of the week resumed its regularly scheduled programming. Tuesday: snail removal duty. I hauled up fifteen gallons of slimy invaders while fending off an irate smallmouth bass who clearly took his parenting duties seriously. I also lost a GoPro-documented race to a turtle who was, frankly, hauling shell. Thursday’s dive was Burlington Bay—more practical than picturesque. Heather and I somehow collected 46 golf balls from the lakebed. The nearest golf course is a mile off. I don’t know either.

So, yes. I’m 54. Getting older. But if I can keep stringing together strange, satisfying weeks like this one, I’ll take another birthday every year.

Even if I don’t tell anyone.