If your shower does not have a built in pump do you need to rely on your immersion to provide the hot water to the shower?

A few more details. What country do you live in? Please explain " immersion". Is it a hot water heater? Why would a pump be needed. To pump what from where? Please repost with more information. Thanks, Tom

I'm perplexed(even though I don't exactly know what the work peplexed means). Okay,so I'm confused. Ive never seen a shower that has a built in pump. Please answer Toms questions and help us all try to figure this out.