You decide to shrink the people to the size of small fish. That should keep them from putting up any more dangerous netting.
As they begin to shrink the people start to scream in terror and try to flee the beach. It is already to late for many though. Many of the birds on the beach begin picking off the bite sized humans. Some humans are also trampled by a dog someone had brought to the beach with them and was chasing the birds.
The dolphin then realized that he had never tasted human before. So he leaped up into the air and created a tidal wave of a splash. When the water hit the beach it drew many people back out into the ocean with it.
The people may have been extremely tiny compared to the dolphin now, but he found that if he scooped enough people up at once he could taste them. They weren't that bad actually, better than most fish thought the dolphin.
He then began to wonder should he ask another creature to bring him more humans if he made the creature larger or make himself even larger to create even larger tidal waves and wash the humans out to sea.