Yes, mammals are largely defined by the features within the egg which could only have manifested on land. But, there are now mammals back in the water - whales etc.

I prefer it when I read God made man

I super disagree with this. This to me is the easy way out, and although it's good to be lazy, evolution is so much more fascinating and beautiful than just saying 'God did it'. The more we learn about evolution, the more beautiful it gets, it just keeps giving and giving inspiration and wonder. 'God did it' is pretty boring and doesn't really clarify anything. We are animals of knowledge and intrigue!