Definition of sorts: bathing together is an act that occurs when two people or more wish to bathe at the same time. This could be sexual or not, but in general, many people enjoy the act.
Whether a shower, bath, or some larger vessel, bathing together can be really fun. It is a great way to learn about your own body or other people. The water can create a nice feeling on the skin, while the steam generates.
Like everything else, it is important to understand that bathing with other people is not an act for everyone. Bathing can be a isolated act for many and intimacy might not be something someone yearns for while doing so.
It is important to talk with partners about what bathing together might look like for you.