Panic in the water usually isn't about not knowing how to breathe, it's about not feeling comfortable yet. Breathing technique helps, but comfort is what actually fixes it.
Watch the video, then try this: at the pool, just get your face wet and relaxed, no pressure to hold your breath long or go under fully. Start shallow, get used to the sensation, build up slowly. The goal isn't performance, it's just feeling okay being there.
Comment below once you've tried it, how did it feel?