45m is well below the range of recreational diving, which has a limit of about 40m. Below that you're looking at needing multiple air cylinders, special breathi

45m is well below the range of recreational diving, which has a limit of about 40m. Below that you're looking at needing multiple air cylinders, special breathing gas mixtures, and decompression stops on the way up. On the other hand, 45m is totally fair game for technical divers, who are trained in deeper, longer, decompression style diving. Divers who pursue this training need to be tip-top recreational divers first.