From Valencia: Caves of San José Guided Excursion and Ticket

The Caves of San José are an unmissable excursion if you're in Valencia. Head to the caves with your guide and explore the area on foot and by boat. Make your way along the longest navigable underground river in Europe and see stalactites, stalagmites, and UNESCO-listed cave paintings.
Depart from Valencia and travel by bus toward the village of Vall d’Uixo where the famous Caves of San José are located.
Before you enter the cave, your guide will provide you with information about the cave system, home to the longest navigable underground river in Europe which is around 3000m long.
Inside the cave, board a small boat and check out the cave system. Look at the stalactites, stalagmites, and UNESCO-listed cave paintings while making your way along the river. After the boat tour, continue on your journey on foot in the dry gallery.
Before returning to Valencia, enjoy 30 minutes of free time in the area to admire the Iberican archeological sights, have a coffee, or check out the souvenir shop.

More details:

On the excursion, you will be able to enjoy an official guide (Valencia&Go) who will accompany you all the way and will tell you the essentials you need to know about Valencia, as well as all the secrets that are hidden inside the Cuevas de San José, its incredible history and curiosities in detail (in Spanish and English).
Once you arrive at the caves, you will board a boat to travel the river in which a guide-boatman will guide you along the way and will point out some key spots of the natural wonder (could be in Spanish).
If you have any questions, you can always ask the official Valencia & Go guide, he will be willing to answer them when you leave the caves.