"This is a Sea Sapphire! And when it doesn’t look amazing it’s invisible! This is a type of crustacean called a copepod. It’s back is covered in guanine crystals. If it weren’t for these crystals the Sea Sapphire would be transparent, but these crystals are spaced in such a way that they strongly reflect certain colors of light. Usually, it reflects blue light, but when the light hits the Sea Sapphire at 45 degrees, it reflects UV light which looks invisible to us."
