Lavender Bay was named after George Lavender, bosun on the prison hulk "Phoenix", which was moored here for many years. You might however be forgiven for thinking the naming reflected the sea of colour of the ubiquitous jacarandas.
This urban mini-park was created by local residents in 1963 in memory of the poet Henry Lawson who lived nearby and penned a poem in 1910 (see the plaque) describing the relatively peaceful view at that time.
Since then, we've acquired traffic jams, giant cruise boats, highrise buildings, the freeway, Wendy's secret garden, big business, Luna Park, the Sydney Harbour Bridge, the Sydney Opera House.
Maybe not everything's changed. Sydneysiders have always, it seems, had a quirky relationship with ferries. In his poem, Lawson seems to be both romanticising and at the same time gently mocking the busy little ferry boats that come nosing round again or glide by at night with their fairy-lights. One of the new Emerald class ferries was originally named 'Ferry McFerryface'! 
The joke wore thin fairly soon, and this ferry was later renamed 'May Gibbs' after a much-loved Aussie children's author, who also happened to live in this area!!
The photo shows the famous 'Ferrython', a popular Australia Day tradition. Our "beloved ferries venture from Circular Quay to Shark Island and then back to a glorious finish at the Sydney Harbour Bridge" (NSW Government website).
This cache has had various forms, from the ubiquitous mint tin to hanging bison tube, a mini lunch box and once again a mint tin.
PLEASE NOTE: At certain times of day, the park can be very busy, so please be discreet. I've provided a very specific hint, to aid with speed of retrieval.
*** FTF Honours go to bella at waggy, redshift, 4Rods, akkatracker. Congratulations! ***