The plants and plant-y things under the waters of the southern temperate oceans of New Zealand and southern Australia...
Ecklonia radiata 'Common Kelp' (Rottnest Island). Can form dense underwater forests. Found from shallow waters down to 25 metres. Widespread in temperate waters of southern hemisphere.
Posidonia sp. 'Strapweed' (Rottnest Island). A group of seagrass with a disjunct distribution; they are found in the Mediterranean and in southern Australian waters.