There is a list of things about sex that people should never need to apologize about. You should never apologize for not living up to some airbrushed body standard. You should never apologize for the wonderfully weird things our bodies do. You should never apologize for size. And you should never, ever apologize for needing or wanting to use lube.
Taking sex off the bed and into new and fun places is an easy way to turn up the heat between you and your partner. You could try the floor, the car, the kitchen table, but one very popular place for sex is in the shower, and for good reason: you're already naked and touching your body, so why not add a partner to the mix? Plus there's hot steam, slippery soap suds melting along your body .... mmmm .... well, you get the idea.