Kirsty Williams-Henry, 27, was hoping to spot pools of bright blue light on the water's surface when she slipped – and fell 20ft onto rocks below.
More than 100 people had gathered on the beach on Saturday night to watch the natural spectacle.
The "sea sparkle" is caused by a Bioluminescent plankton called Noctiluca scintillans which shimmers a bright blue light when it is disturbed.
Kirsty was admiring the glow from the breakwater on Aberavon beach in Port Talbot, South Wales, when she lost her footing and plunged onto the rocks below.
It took coastguard rescue teams two hours to help her in a race against time before the tide came in.
Jules Newton, who called 999 after Kirsty fell said: "My sister and I called the emergency services, we were a few feet away. She did fall onto rocks. The call handler told us to tell everyone we saw to stay away from the pier until the police arrived.
"Horrific accident my thoughts are with her and her family.
"The pier is treacherous. I'd avoid and just paddle at the waters edge."
A spokesman for the coastguard said Port Talbot and Porthcawl coastguard rescue teams both attended the incident.
What causes this phenomenon?
The bioluminescent plankton responsible for the glowing sea are called dinoflagellates.
The phenomenon typically occurs in warmer climates, but because of the recent heatwave the UK has been experiencing, it has been spotted in Wales.
The warm weather has lead to a rapid increase in the rate that the plankton grows and also reproduces.
The phenomenon will only occur if there are more than 100,000 cells of algae in just a litre of water and it has been a very sunny and warm day, allowing the plankton to "charge up".
The glow is produced when oxygen reacts with luciferin and luciferase and energy is created which generates light.
The algae normally has a blue hue, but can sometimes appear to be green.
The plankton doesn't glow all the time, during the day the plankton appears to be rusty-brown in colour and only glows when it's disturbed, for instance, when waves crash into the shore.
Scientists also say that calm seas can result in an increase in the bioluminescent algae as large quantities of the algae can become trapped in coves or bays.
Now, while this phenomenon is fairly rare for the shores of Wales, it is a regular occurrence in warmer climates, such as Puerto Rico and the Maldives, with some countries marketing the phenomenon for tourism purposes.
They were called at 11.04pm and spent around two hours at the scene.
A spokeswoman for South Wales Police said they assisted in the rescue of a woman who had fallen approximately 20ft from the pier.
She said: "Officers were called to the scene shortly before 11pm alongside the Coastguard and ambulance service.
"A 27-year-old woman was subsequently taken to the University Hospital of Wales with multiple injuries."
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