Indonesian H.erectus were semi-aquatic early-Pleist.:
• Archaic Homo's atypical tooth-wear caused by "sand & oral processing of marine mollusks" Towle cs 2022
https://onlinelibrary.wiley.com/doi/10.1002/ajpa.24500
• H.erectus s.s. = coastal sediments, e.g. Mojokerto barnacles + corals, Trinil Pseudodon + Elongaria (edible shellfish), Sangiran-17 "brackish marsh near the coast".
• Stephen Munro discovered sea-shell engravings made by H.erectus, Joordens cs 2015 Nature 518:228–231
https://pubmed.ncbi.nlm.nih.gov/25470048/
• Ear exostoses (H.erectus & H.neand.) develop after years of cold(er) water irrigation
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5696936/
• Pachy-osteo-sclerosis = slow+shallow-diving tetrapods (de Buffrénil cs 2010 J.Mamm.Evol.17:101-120), e.g. erectus’ parietal bone is 2x as thick as in gorillas.
• Brain size in erectus (2x apes-australopiths) is facilitated by aquatic foods, e.g. DHA docosahexaenoic acid in shellfish… cf. Odontocetes, Pinnipedia, Enhydra.
• Platycephaly in erectus/neand.: long, flat, dorsally-shifted brain-skull = hydrodynamic streamline, google GondwanaTalks Verhaegen English
• Pleist.descendants/relatives colonized islands far oversea, e.g. Flores, Luzon
https://www.academia.edu/36193382/Coastal_Dispersal_of_Pleistocene_Homo_2018
• Homo’s stone tool use & dexterity is typical for molluscivores, e.g. sea-otters