If you notice that your shower water smells fishy, there are a few potential explanations. First, the problem could be with your water supply. If you have a private well, it's possible that there is bacteria in the water that is causing the fishy smell. Alternatively, if you're on a municipal water supply, the issue could be with the pipes leading to your home. If they are old or corroded, they could be leaching metals into the water which can cause it to smell fishy. Finally, it's also possible that the problem is with your drain. If there is standing water in your shower drain, it can start to develop bacteria which can give off a fishy smell.
If you're concerned about any of these potential problems, it's best to contact a professional for help. They will be able to test your water and diagnose the problem so that you can get it fixed quickly.