Hey there@ Speaking as a fellow new diver let me share some of my experiences and what I learned about them. On my first open water checkout dive, I had a similar panic attack. When I first started under, saw nothing but murky blue water. Couldn't see the buoy line, none of the other divers or my dive buddy. It took me surfacing, and reorientating myself to calm down. One thing that helped me, then and since...is to keep a visual reference point. In my case following the line down gave me something to focus on and judge my descent rate.
During the rest of my dives, I have noticed a short period of time of increased air consumption before I calm down and get into the flow of my dive. The factors I have noticed are the more familiar I am with the location or dive conditions, this effect goes away. My advice to you would be to take your time. No need to rush....get comfortable before going further in your dive. Also, try to follow a downline and stay close to your buddy. The more you dive, the more familiar and comfortable with your gear and skills you will become. Before you know it...you might not even remember having those anxiety attacks =)
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