Sun bathing is one of the things which allows you just to lay and rest or reading your book in piece while enjoying the light of sun. Lunak have been quite a lot under the sun lately, so much in fact he probably have got fluffy from the sun bathing so he couldn't enjoy the sun on his scales no more but rather keep himself warm with his fluff.
Norna on the other hand didn't have any shapeshifter capabilities like Lunak did, but she decided to give him something better at the beach than sunbathing session. And it looks like Lunak really liked his consolation gift he decided to unwrap it a bit more than she was looking for. Though she liked this sudden turn of tables getting herself more than a nice bellyful relief after stressful days before that