Vision sharing is an exceptionally strong and rare psionic ability that is seen only in Mako: Island of Secrets.
Vision sharing is a power shared by merpeople siblings. Throughout the second season of Mako: Island of Secrets, Zac and Mimmi have been able to see what the other was seeing and feel the emotions that the other is feeling. In "Discovery", Mimmi saw the same vision that Zac had while Sirena was using her Moon Ring on him. In "Awakening", Mimmi was able to see what Zac was seeing while he was in a full moon trance. In "Supersized", Zac saw what Mimmi was seeing when she was in trouble and said he could even feel how scared she was. It is unknown why the connection only started happening when she and Zac met.
It is unknown why only Zac and Mimmi share these abilities.
This could also be a branch or an advanced version of a sibling sensing power since Sirena said she could always tell when Aquata was near from feeling the water