Segmented or Ringed Worms belong to the phylum Annelida. Most of the members of this phylum are marine animals. What we will have in this category is mostly Earthworms or Leaches.
The specimen appears to have annuli, and four dark dorsal stripes, the median pair of which are close and separated by a fine pale line. I am unable to determine details of the number of eyes and so on from the photo. A freshwater leech. Swimming leeches are generally flattened, as you noted.
1,900,751 sightings of 21,152 species in 9,355 locations from 13,000 contributors CCA 3.0 | privacy
We acknowledge the Traditional Owners of this land and acknowledge their continuing connection to their culture. We pay our respects to their Elders past and present.