Nature lovers were left horrified as they watched a group of jet skiers apparently speed towards a pod of dolphins playing in the mouth of the Tyne.
Northumbria Police is investigating reports of people on jet skis "harassing" dolphins near North Shields Fish Quay, just after 8pm on Thursday.
The incident was captured on video by a witness who claimed three people on jet skis had appeared to turn intentionally in the direction of the marine mammals.
She said: "This was truly shocking to watch and appeared a deliberate act as the pod was very obvious.
"They steered towards the dolphins and went straight for them where the last dolphin had only breeched seconds before. This was appalling behaviour and so so upsetting."
A second woman said she had seen the incident while watching the dolphins with her daughter.
She said: "I had to stop video as my little girl was so upset she screamed 'they are going to hit the babies', as the dolphins had their calves."
Dolphin expert Dr Ivor Clark, who runs Newbiggin by the Sea Dolphin Watch, said the footage had left him "very very angry".
"Generally dolphins are good at avoiding vessels, the problem with jet skis is their manoeuvrability, they can turn very very quickly and even with their capabilities dolphins can't always move quickly enough to get out of the way," he said.
"I could foresee this happening simply because we have so many dolphins here now, and when you combine that with the fact that they are coming closer and closer to shore, there is a risk. Dolphins have long memories and, at the end of the day, it's negative human activity that will drive them away.
"This probably isn't going to go away and it will potentially get worse until the authorities clamp down on it."
Northumbria Police said the force is investigating "any possible criminal activity including potential speeding laws being broken or wildlife laws" as a result of the incident.
Acting Marine Sergeant Paul Spedding added: “Everyone has a responsibility to protect our wildlife and anyone found to be in breach of any laws will be prosecuted.
“It is illegal to harass, feed, chase and touch Marine mammals in the wild and we’re urging all water users to be vigilant and respectful. “If dolphins do approach you then maintain a slow, steady speed and refrain from turning back towards them.
“Keep your distance and never get closer than 100m and if you’re unsure of their direction then simply stop and put the engine in neutral.
“Human interaction can have devastating effects on wildlife so we are reminding the public to enjoy from a safe and respectful distance so others can enjoy them too.”