That question has inspired biotechnologists to develop a new type of sun protection that's made from the same amino acids found in some fish mucus, algae and bacteria. Potentially, it's fish goo for the skin.

The scientists involved say this sunscreen is not only biodegradable and natural, it's more stable and actually works better than the inorganic gloop you smear on your skin every summer.

One of the researchers, Professor Vincent Bulone at the University of Adelaide, told Fairfax Media that the newly developed compound also has potential commercial application for furniture, in cosmetics and shampoo, and in some medical procedures.

So how does it work?

Fish and many other species can swim around in the sun all day because they are naturally protected from damage caused by the sun's ultraviolet radiation.

Different fish species use different methods but some use a family of amino acids to block out damaging radiation from the sun.

Professor Bulone and other scientists at Sweden's Royal Institute of Technology were able to extract the UV-resistant mycosporines and attach them to a lattice derived from the shells of crustaceans and insects.

Professor Bulone is the new head of the ARC Centre of Excellence in Plant Cell Walls at the University of Adelaide.

"In our work we have exploited the same type of mycosporines produced in many fish species of the Great Barrier Reef to protect their eyes and tissues from UV light," Professor Bulone said.

If developed commercially for sunscreen the bioengineered molecules could replace inorganic nanoparticle compounds such as titanium oxide and zinc oxide.

Known as "mycosporine-like amino acids" (MAA for short), the natural UV-blockers are conjugated, or bonded with, a biopolymer matrix, called chitosan (CS).

Researchers found that the resulting "CS-MAA conjugates" are "efficient against both short-wavelength UV-B radiations responsible for ... sunburn and long-wavelength UV-A radiations".

In their paper published this week in Applied Materials and Interfaces, Professor Bulone and others also found that CS-MAA conjugates take longer to break down in the sun than conventional sunscreens.

Professor Bulone told Fairfax Media that the polymer chains made by this new compound could potentially be incorporated into shampoo to protect dyed hair from UV damage.

He also said that the anti-bacterial properties of the transparent films could be developed for the healing of burnt skin or for post-operative protection of wound dressings.

Other possible applications include film coating of car dashboards and plastics or in paints for sun protection.

Professor Bulone is effusive about the potential of the CS-MAA matrix. He says the bonding is so efficient that the mycosporines only use about 3 per cent of the amino acid groups on the chitosan lattice. This means there is potential to bond them with other biologically active compounds.

So when can we pop to the chemist for some sunscreen with fish mucus in it? "That depends on when we have a commercial partner interested," Professor Bulone told Fairfax Media.

"We've been in talks with one well-known company and they are interested to develop this research for use in shampoo and creams."

And while it's still too early to be discussing what SPF rating the compound could provide, Professor Bulone said that its UV-absorption rates are 2½ times above what is considered suitable for sunscreen applications.

He said: "We have not made a physical cream yet, but we have made transparent films with the materials and these have unique properties: they are resistant to heat, stable and non-toxic. And, of course, they have a high absorbing capacity in both UVA and UVB range, which is not the case on individual compounds currently used in sunscreen creams."

The idea of applying fish mucus to your skin might be a turn off for some, but Professor Bulone is reassuring.

"For this process to be commercially viable, we won't be able to use the fish mucus or algae amino acids," he said. "The best way to develop the mycosporine-like amino acids in large amounts is through developing genetically modified bacteria in fermentors."

So that's all right then.