Natalya Scudder -- a star on season 7 and season 8 of "Below Deck" -- says she spent the night in disgusting digs at a detention center before being deported from the USA.

We spoke to the reality star and influencer earlier this week ... and she told us all about her nightmarish experience -- which began when she was detained by authorities over photos she took in the USA during her last visit.

She says she was told cashing in on the snaps as she had meant she needed a different kind of visa than the one she applied for ... at which point she says they took her to a dirty room and told her she'd be staying for anywhere between 1 and 5 days.

Watch the clip to hear Natalya describe the rough accommodations ... from the lack of towels to the dirty bedding.

Eventually -- after a rough night -- she says she was taken in for an interview and promptly deported ... sent back on a plane to Australia. She says it was a 17-hour flight there, 30-40 hours in lockup and a prompt 17-hour flight home.

While she loves America, Natalya says authorities are cracking down ... and she warns her fellow influencers to be very careful when traveling through the country.

After all, they don't want to end up below decency like these authorities allegedly subjected her to!