Hard time breathing in swimming pool?

So, today I had my first swimming lesson. They told us to walk in the water towards the side with our chin touching the water. I had a really hard time breathing here and my chest felt tight. I had to force the air to go through. When my head was out of the water, I was completely fine. I don't have asthma and I've swam before so I don't think it's a phobia. Although, I've been worried about water getting in my eyes since I wear contacts and it worries me. In fact, water went into my goggles this morning. Is something wrong with my lungs?