It's not recommended to use Iona Mineral Core Tile in your shower.
While Iona tiles themselves are 100% waterproof, if the click mechanisms on each tile are not perfectly installed, they won't achieve a 100% seal against water. Occasional spills and splashes are fine, but prolonged exposure to pounding water (like from a shower) has the potential to lead to water accumulation underneath your flooring which can lead to mold growing on your shower subfloor.
No amount of water will hurt your Iona flooring, but mold growing underneath your flooring can be detrimental to your health. Therefore, we do not recommend using Iona as a shower tile.