Residents of Melbourne's Brighton beach were astonished to discover a leopard seal basking on the shoreline yesterday. It follows a string of similar incidents in Sydney and Tasmania. Needless to say, attempting to approach these large predators can be dangerous - but did you know it's also illegal? Apparently, it's an offence to be within a whopping 30 metres of all seal species.

Of all apex predators, the white shark Carchardon carcharias (commonly known as the great white) is perhaps the most fascinating. The potential danger from (very rare) human interaction has embedded the species in our national consciousness.

New research has used genetic analysis in a world-first effort to accurately estimate Australian and New Zealand white shark numbers. The size of the total adult population might surprise you.

On the back of the news that Victoria will be banning plastic shopping bags, I wondered how much plastic is actually in the ocean. I always hear big, crazy numbers and I've certainly seen the pictures but what is the reality? The science? How does it affect ocean life?

This infographic explains.

Why is the sea salty? The short answer is that water dissolves the salts contained in rocks, and these salts are carried in the water to the sea. We take a look at the science.

Brief news items of note for Lifehacker readers, including: Australian scientists prove acupuncture relieves pain, the strange underwater creatures found 4km down in the abyss off Australia, can you survive the Game Of Thrones TV quiz?

You've probably heard that you're supposed to urinate on a jellyfish sting, or perhaps pour alcohol on the affected area before scraping the stingers away. But a recent study suggests most of those home remedies, including the golden shower, don't work. And some of them can actually make things much worse for the victim.