What I don't understand is sometimes when I ride big waves I find that I'm going so fast that I'm worried if I turn I'll just lose control. The board is going so fast it's skipping across the water. It feels like it just wants to go straight. I try to turn and bury my toes into the deck but I'm going so fast that the rail just won't sink.
I find I have to go far into the flats where I lose speed and then do a bottom turn at a speed I'm used to, and where I feel in control. I'm sure there is a proper way to do this as good surfers can turn on the rail at incredible speeds with a huge spray coming off the turn.. but I can't

I can't blame the board as it happens to me on my 6'4" and 6'0 shortboards and also on my 6'0 fish. I know I can bottom turn correctly at normal speeds but what's the trick when you are skimming along so fast that the board is actually bouncing a little. I tried pushing harder on the tail but I found it started to wobble out when I did that once.
It only happens on certain big steep waves that have a fat shoulder so you have to ride the wave straight to the bottom before going down the line. This creates a lot of speed. On regular big waves I find I'm slightly more angled as I have to speed down the line to avoid the close out and I don't get the same problem.
Anyone have similar experiences or know what to do?