The reality star pair have been growing close in the house, frequently cuddling and kissing… and on Monday night's episode, they take it one step further by sharing a "romantic" shower.
Just a shower, mind, as Marnie points out…
The Geordie Shore star gushes: ""I just had the most romantic shower in my life! I would never do anything more than shower with him and kiss him.
"I've never had a boy treat me how he treats me! I feel so lucky. He is just perfect. I don't ever want to leave this house!"
Lewis is certainly keen on Marnie too, revealing on last night's episode he wanted to defend her honour after Heavy D made comments about them hiding alcohol away.
"I wanted to show Marnie I cared and I was man enough to stand up to a big lump like that geezer is," said Lewis. "I had absolutely no intention of attacking him whatsoever but I wanted to prove to Marnie I wouldn't let another man stand there and say things that are bulls**t."
Could Marnie and Lewis have a future?!
Lewis' former TOWIE co-star Billie Faiers thinks their feelings are real but perhaps it won't last in the real world. "I don't think it's a showmance because they're both single and they probably both really fancy each other," she told us.
"Whether or not it will be something bigger when they both come out, I don't know. I don't think it will and I think it's just a bit of fun in the house. You spend so much time with people in there, it's inevitable that might happen."
Marnie will no doubt be hoping Lewis isn't evicted this week, then. He's up for eviction alongside Stephen Bear, Saira Khan and Heavy D.
CBB airs 9pm on Channel 5.