Most of the diving you will enjoy on holiday is going to be from a 'normal' daily diving boat but there may be some instances where you want to do a drift from the zodiac, so you will need to 'perfect' the backwards roll. It's very simple so long as you remember a few key points.
There are two ways of doing this:
Positive entry
Make sure you have some air (at least half full) in your BCD, then holding all equipment in place as you would for a Giant Stride, right hand on your mask and regulator and your left hand holding your weight belt and pressure gauge. Then position yourself with your tank on the outside of the rubber tube from the zodiac and when the zodiac driver or dive guide gives you the go signal make a gentle backwards roll. The buoyancy from the BCD will make sure you come safely back to the surface. Give the driver and dive guide the OK signal then on with your dive.
Negative entry
This one's a bit trickier. The idea for the negative entry is to swim straight down to a predetermined depth as soon as you enter the water. This is mostly used to overcome any surface currents that can occur at shallow depths.
Empty all the air from your BCD using all of the dumps on your jacket. Then it's the same procedure to enter the water as before.
Once you feel your face hit the water then start to fin downwards. If you have a rear dump valve on your BCD it's also a good idea to reach back and pull on it so you're sure that all the air is released from the jacket as you descend. Don't forget to equalize!
Stop when you reach your predetermined depth, then, once you've made contact with your buddy or dive guide continue the dive as planned.
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