Time to break out the PADI RDP (or even the PADI eRDPml), everyone!

22m for 35 min should leave you PG-R.

SI for 45 mins then takes us to PG-I.

Flip over to Table 3 and intersect I with 16 metres. 

You'll see the white box indicates the RNT will be 29 mins and now it's time for the A.R.T. of dive planning!

A=Actual Bottom Time - 36 mins

R=Residual Nitrogen Time - 29

T=Total Bottom Time 36+29=65 minutes.

All gases will affect us differently when breathed under pressure and Helium, commonly used in deep Trimix dives, is no different.

Manifestations such as tremors, headaches and involuntary twitching can occur but this reserved for depths of approximately 100m/sw or deeper. 

In Section Three of the Advanced Open Water Course Guide of the Instructor Manual, there is a really great quick reference great table. This includes which Instructor may conduct which Adventure Dives, what materials are required and the minimum age of participants in the Adventure Dive itself.

Think of this as the AOW Key Standards.

This question wants to know the difference between the objects downward force; its weight and its upward force; the displacement. The fact that the object is heavier than the water it displaces means it is negatively buoyant and to move it we must first make it neutrally buoyant.

Since we need to find the volume of air to be added to the lifting device we need all numbers converted to litres. the weight of the object; the anchor weighing 22 kgs must be divided but the type of water it is displacing. 22/1.03=21.36 (rounded to 2 DP)

This is the total volume of water that needs to be displaced to lift the anchor. Since we already have 18 litres of displacement in our favour already we subtract that from the total required, 21.36-18=3.36. 

This is the amount I need to fill a lift bag with to remove the anchor from the bottom. 

Semi-Closed Units generally supply one breathing mix at a time. The gas enters the breathing loop at a constant rate so oxygen in the mix may be replenished as the diver consumes it.

Excess gas must be constantly vented from the loop to keep the gas in the breathing mix correct. Inert gas and breathing gas cannot be separated making it inefficient in the oxygen reserve.