Deep learning is here to stay and has revolutionized the way data is analyzed. Furthermore, it is straightforward to get started. Recently, I played around with the fastai library to classify fish species but wanted to go further behind the scenes and dig deeper into PyTorch. As part of another project, I have used a U-Net to perform semantic segmentation of ‘pike’ in images. Training has been done on Google Colab and a local GPU powered workstation excellent for smaller experiments.