Growing in shallow (15 cm) water.
Species ID unresolved: ambiguous - Plants have characteristics that (individually) are associated with M. variifolium (glabrous stem, leaves per whorl), M. crispatum (leaf length) and M. simulans (glabrous stem, colour of styles, colour shape mericarps).
I don't know enough about them to say Yes or No or Maybe. the treatment of Myriophyllum by Orchard is sprinkled with caveats about the challenge in distinguishing between certain species, and especially the need for mature fruits, and their surface ornamentation. For many water plants, vegetative characteristics are fairly plastic, and so species tend to overlap (eg whorl number). Although flowering, these are young plants, having grown in last 3 weeks in response to November-December rain (no milfoils observed 3 weeks ago). Previous surveys records (via ALA) have recorded "Myriophyllum sp.". Am hopeful that species ID will be clearer later in summer.