Scientists have posted jellyfish spotters on Irish Sea ferries to study a breed with a painful sting which could swarm along the Welsh coastline.
Very little is known about the mauve stinger
Swansea University marine biologist Dr Jon Houghton has been given £50,000 to find out how many mauve stingers there are between Wales and Ireland.
The small purple jellyfish recently wiped out £1m worth of salmon at fish farms in Northern Ireland.
Known as pelagia noctiluca, they have a wasp-like sting and glow in the dark.
Swarms of the jellyfish, which vary in size from a 10p piece to the size of a clenched fist, have affected Mediterranean beaches.
They are small enough to drift through the mesh of salmon cages and in November 2007 billions in a layer 35ft (10.7m) deep and covering 10 square miles of water wiped out 120,000 salmon in a fish farm in Glenarm Bay, Antrim.
This was the first major infestation of the mauve stingers affecting British waters and scientists suspect that global warming is probably the principle cause.
The Natural Environment Research Council has given Dr Houghton the emergency grant because there are fears more blooms of the jellyfish around British waters could be problematic, particularly in the summer months.
Researchers began going out on ferries leaving from Fishguard, Holyhead, Larne, Rosslare and other ports around four weeks ago.
"The trouble is that we know so little about these jellyfish," said Dr Houghton.
"Until recently, they were viewed as bags of water that had little or no impact on our ecosystem.
"Now we need to learn, very quickly, about their behaviour and about their breeding patterns in our waters.
"We need to get some basic data about numbers, and the easiest and quickest way to do that is simply to send researchers out on the ferries.
"For the past few weeks, they have been standing on deck looking at the sea and counting jellyfish. That is how we are getting a baseline figure for their numbers."
The work will be followed up in the coming months by biologists who will sail on British research boats in the Irish Sea and north Atlantic in an attempt to determine numbers and health of the mauve stingers.
Researchers will also fly over coastal areas to study jellyfish blooms.