Pretrained UNET for satellite images

Hi, I’ve just started the book (finished chapter 1) and would like to try a DL model for my work, trying to map small on-farm reservoirs (SRs) in satellite data. I’m thinking I should start with a UNET (but maybe down the line I should consider LSTM for taking into account the temporal dynamics of these SRs, of holding water during the wet season and drying up or decreasing in size during the dry season).
Does anybody know where I could find a pretrained UNET for this? Even if only on ImageNet? and would you be able to point me to code to get started?
Thanks so much, Mirela