On My Sunrise Swim

On my sunrise swim saw a tern in its swallow like flying tapestry drop like it was shot and go down into the water. Immediately he popped up with a fish and greedily guzzled it, midflight. I have read that they will poke with their beaks at the head of any intruders to nesting sites---I wonder if they are tempted to do so also in the guarding of their cuisine? As he dived quite nearby (I was in deep water) I thought of that possibility.