Although sound travels through water at approximately 4 times it travels through air because of it's increased density, temperature and pressure are also factors. This is how whales and porpoises are so proficient in communicating over large distances underwater and why the use of seismic airgun blasting is such a threat to all marine life.
Although general standards pertaining to PADI Specialty Programs can be found in the Key Standards table in your PADI Instructor Manual, more details can be found in the individual Specialty Instructor outlines.
The hydro testing diving cylinder should be carried out in accordance with local laws and regulations or if the cylinder has been damaged, heat treated or has any external damage that can affect the cylinders integrity.
Stonefish stings can be extremely painful and in some cases lethal. The application of heat and anti-venom are the most effective first aid steps and hot water, no hotter than 45 degrees Celcius applied to the affected area will destroy the Stonefish venom although it may cause additional discomfort to the patient.
As listed under table 3 of your RDP or on the inside lid of the PADI eRDPml are the rules for dealing with emergency decompression.
If a diver accidentally exceeds their NDL by no more than 5 minutes the following applies.