Mystery surrounding a substance spotted floating in the sea at Portobello beach in Edinburgh has been solved.
The sea squirt shares 80% of its DNA with humans
Thought initially to be sewage, it was reported by members of the public after a spell of bad weather and rough seas.
However, an investigation by the Scottish Environment Protection Agency (Sepa) drew a blank.
Sepa has now concluded the substance was sea squirts, a kind of larva that feeds on plankton and attaches to rocks and kelp.
The sea squirts has a rod running down its back which it is thought could be the forerunner to all vertebrate backbones. It shares 80% of its DNA with humans, birds and fish.
After hearing of a complaint about waste floating in the water at Joppa, Sepa officials visited the site along with Scottish Water colleagues.
Owen Foster, one of Sepa's investigating officers, said: "It was important to establish what had been seen but there was nothing apparent when we were on site.
"We went to the beach at both high and low tides over a number of days, but we couldn't find any trace of sewage."
Sepa's ecology team joined the hunt, with their explanation providing the final piece of the puzzle.
Calum Duncan, Scottish conservation manager for the Marine Conservation Society said: "I commend the diligence shown by Sepa to get to the bottom of this mystery.
"The species of sea squirt recorded is among the most common and found all round Scotland, including low on the shore at Joppa and other rocky areas in the Forth."
Mr Foster stressed the public "are our eyes and ears around Scotland".
"On this occasion it was sea squirts, but the next time it might not be," he said.
"If people are not sure what it is and they call us, we will go out and investigate."
Sepa's 24 hour pollution line can be contacted on 0800 70 60 50,