Each compartment is named for the time it takes one halftime to complete. A tissue that has is 75% saturated has completed two halftimes, this means if it is a 60 min compartment it would have taken 120 minutes to fill those compartments. 

I know you're all fluent in Greek so this one should be pretty simple. Hyper means too much and Kapos means smoke or for us, carbon.

Carbon Dioxide is a primary trigger for the breathing reflex so it's important for our body to regulate how much is in our bloodstream. We can become HyperCapnic during diving by skip breathing, overexerting ourselves or by using poorly maintained equipment. 

Rescue exercise 4 may be performed in confined water prior to being completed in open water. When performed in open water the exercise which is essentially a three-part skill; responding to a diver making an uncontrolled ascent, being overexerted and signaling out of air, it has a maximum depth as listed in the 2018 PADI Instructor Manual of 18m. 

There is a printing error on some slates indicating that the maximum depth for Rescue 4 is 6m. This was corrected in a Training Bulletin in 2016. 

Constants to PADI physics questions are always listed on them. It states that every metre of fresh water equates to 0.097 ATM of pressure. 

Multiply that by the given depth (40x0.097=3.88) and add 1 ATM for the air atmosphere and you get the correct answer. 

Slack water is when the tide is 'unstressed'. meaning it is neither coming in going out.

This means there is a drop in water movement causing currents, making entries and exits simpler for shore dives. Slack high tides can also bring upwelling of clearer water meaning improved visibility too.