I purchased an organic "extra firm" foam mattress from a big box store and I could sink my hand right into it. I returned it and in my research came across this one. I thought it was a bit pricey but that it would be worth it for the peace of mind a safe mattress can bring. 

I'm really happy with this mattress! Excellent firmness, no smell, easy to lift and move. I love that it is dual sided and can grow with my baby so we can get years of use out of it.