Five couples swap partners for 3 weeks essentially living as married couples while doing so. Without the sexual activity for the most part, though some couples do get tactilely intimate.
Obviously this disrupts the various relationships and the outcome is pretty predictable. I wouldn't necessarily call it toxic since all it is doing is exposing the nature of human interaction on a very personal level. True, some people consider this a societal low, but realistically its really only exposing human nature in a very blatant manner, stripping away the the underpinnings of intimate relationships for all to see.
Actually I think it's quite a healthy way to explore the realities of serious romantic partnerships; especially since so much of what constitutes healthy pair bonding is really undisclosed misinformation with honesty and truth buried under pretence, façade and fluff.
Having said this, I'm not sure it's for everyone. If you don't want to colour your notions of love and romance, or explore the reality of what exists under the covers of perceived romance, then give this a miss. Even though it isn't uncouth, dirty or 'for the most part' tasteless, it is pretty raw in places with notions of love and compatibility unearthed for the reality of complexity that actually exists between the various couples.
I liked it, no real surprises, and exactly what you'd expect from a modern reality series. In fact given what's on offer, its actually a pretty good production.