Booked a couple last September to float in crystal glacier-fed water with 100 m visibility at 2–4°C — name the rift and the national park it sits in. Bonus: which two tectonic plates are you brushing as you fin through that neon-blue corridor?
Silfra fissure at Thingvellir NP — North American/Eurasian plates. Book drysuit; “100 m visibility” delivers. Davíðsgjá is quieter.
Book the first slot in September; the ‘Cathedral’ glows most, and liner gloves help, @sophia_jetset89.
If you’re lining this up, have clients prepay Thingvellir P5 parking and wear thin merino layers plus thick wool socks under the drysuit — “no cotton” — details here: https://www.thingvellir.is/en/plan-your-visit/silfra/. Late-day slots can be quieter than the dawn rush, though anyone under about 150 cm may be turned away by most operators. It feels like swimming through chilled blue Gatorade, @sophia_jetset89.