This special mutation tends to happen when a human female body gets infected whereas human males tend to turn into Oozes. The creation of Sea Creepers would be T-Abyss adapting the host's body to its surroundings, noticeably where Sea Creepers are found in large bodies of water (flooded rooms). In a special case where one female infected with T-Abyss was nowhere near a large body of water the individual became a rare type of Ooze while retaining certain a slight form.
The carapace resembles a woman's long hair which covers the entire body, reducing friction and allowing them to move freely underwater. It enables them to creep around the water silently. As soon as these monsters approach their targets, they spread their six human-like arms which they use to hold their prey while they bite into them.