Phrase: Tongue in cheek
As we can see in the picture, it is a beautiful day for snorkelling.
Well, it is a terrible day for snorkelling, but I was speaking tongue in cheek.
Sometimes speaking this way may seem a little like sarcasm, but the difference is that sarcasm is intended to hurt someone.
When someone is speaking tongue in cheek, they are joking and don’t intend to harm anyone.
They may sound serious, but they are joking.