Today we’re going free-diving in a “Blue Hole“, where fresh and marine water meet, in the middle of the island. Unfortunately the water has a greenish cloudiness and the fish diversity is very limited too. But free-diving in this green soup reminds me of free-diving in the blackwater of the Rio Negro. You leave the surface and enter a bottomless eternity, diving deeper and deeper, seeing neither the surface nor the ground, until finally contours reappear.
Swimming upwards you can lose your bearings. You exhale to see which direction the air bubbles are rising. That must be upwards. But it’s a weird feeling when the bubbles rise to the left and you have to follow them, although your feeling tells you that isn’t the right direction!
After free-diving it’s time for some research: light measurements at the water surface and under water. Although Chris is a free-diving world champion he’s not an expert on aquariums. He is impressed with us as we measure and test and helps us as much as he can. He can, for example, effortlessly stay motionless holding the sensor at a certain depth under water until he is told to come up again. Our PAR measurements which indicate photosynthetically active radiation are particularly interesting. The newly developed JBL LED aquarium lights have very high PAR values. They will therefore prove very useful for marine aquarists since corals receive the same radiation in the wild as aquatic plants! We only start to experience the famous blue light at a depth of 8 metres. And no one has an aquarium that deep!