St. Johns River

Tides cause seawater to enter the mouth of the St. Johns River and can affect the river's level into the middle basin. As a result, much of the river in Jacksonville is part seawater, making it an estuarine ecosystem. The animals and plants in these systems can tolerate both fresh and salt water, and the fluctuations in saline content and temperatures associated with tidal surges and heavy rainfall discharge. Marine animals such as dolphins and sharks can be spotted at times in the St. Johns at Jacksonville as can manatees. Fish such as mullet (Mullidae), flounder (Paralichthys lethostigma), shad (Alosa sapidissima), and blue crabs (Callinectes sapidus) migrate from the ocean to freshwater springs upriver to spawn.

Question: are there dolphins in the st johns river
Answer: yes