AventuraXtrema is the reason San Bernardino is worth more than a lakefront lunch. They run fourteen activities around the lake, every day of the year, with certified kit and their own guides: tree-top ropes courses, quads, 4x4, the bola loca, canoeing along the shoreline in front of San Ber's grand old houses, mountain biking, a climbing wall, boat trips, a pendulum jump from the tower of the amphitheatre, water-skiing, archery, a scenic flight over the lake, and a snake-conservation project called Proyecto Boa.
The strange one, and the good one, is the diving. A quarry near Ypacaraí was worked through the 1960s until the diggers cut an underground water vein and flooded it; what is left is a lagoon fifteen metres deep with the quarry machinery still standing on the bottom. Gs 500.000 buys you the dive with everything included — certified divers get an hour, and if you have never dived before you get a thirty-minute baptism with an instructor beside you. Minimum age twelve, book two days ahead, maximum five people per departure.
They are a PADI centre, so you can also take the certification here, from Scuba Diver and Open Water up to Rescue and Master Scuba Diver. The entry requirements are exactly what you would expect: ten years old, swim 200 metres, float for ten minutes, fill in the medical form.
Everything is booked over WhatsApp — every activity page ends with a button that opens a message to them. The office is on the pedestrian street in San Bernardino, and the dive meets either there or at the quarry.