Blue sponge, Haliclona or Xestospongia sp.
Introduced on the 15th May 2021. I'm not sure of the species, apparently Xesospongia feels harder and firmer to touch than Haliclona but since I avoided touching it at all I have no idea if it's soft or hard. Both are commonly available. The top down shot illustrates the actual colour of the sponge best.