Plant-based tung oil is one of the oldest ways of preserving wood and still the best.  It penetrates the wood, prevents mold from growing and brings out the rich beauty of the wood grain. Used with a natural no VOC citrus solvent, it can be applied to floors giving them a rich deep sheen without that plastic looking shiny coat that most sealers have.

You will need to apply several coats.  The first coat should be thinned with 50% citrus solvent. The successive coats should be less thinned, and the last coat 100% tung oil.

Sand each coat with 320 sandpaper before applying the next, so the next layer will bond.  Sand  lightly to avoid sanding through one a previous coat. Ideally allow a week between coats, although one or two days might suffice in warmer weather with proper air circulation.  Tung oil has fantastic resistance to water, mold, bacteria, yellowing, darkening, and offers strength and flexibility.