Fear of God's power, or fear of what I would become without God?

So my parents brought us to Batam for CNY. There was one night where we were swimming in the pool at night. Everyone was at the shallow end of the pool, and I wanted to do laps. At the deep end, there was no one, and as I approached the end, it was dark and murky. I was afraid. Really scared. Of I don't know what. Water monsters?

 I told myself, you shouldn't be afraid. God is with you. You have no reason to be afraid.

But i was still scared.

Was it because I know that I haven't been praying regularly?

That deep inside me, I was afraid of what i would become without Him?

That without God, I'm just a courage-less human without security?

Is this the "fear" that the bible often talks about?

Or would the fear often described be used to describe fear of God's mightiness and what he is capable of?