Hi Neil, thanks for taking time in giving us your review.
We do not go deeper than your dive certification level, so if you are certified as an Open Water diver, we will not take you deeper that 60 feet/18 mts, that you where train for.
We do 60 min dives unless someone in your group had less air. We do small groups because of this, but maybe you where way better on air as the rest of your group and it can be than after 60 minutes you still had air left (maybe you are really good on air!).
But we are glad to know that you still enjoyed your dives with us.