A small certified-diver operation running a daily double dive off the island of Barú: boat out at seven, back by noon, COP 460,000 a head with all the kit and a guide in the water. They also run the whole PADI ladder from Discovery Scuba through Rescue.
What they do not do is publish an address. The booking happens on WhatsApp and you are told where to meet, which is normal in Cartagena and irritating if you like to walk in and look at the compressor first.