Hydra (Dragon Eye Book 2)

Deep in the Scottish Highlands, near the shore of Loch Ness, lies Nattertinny Castle—whose name, in Gaelic, means “dragon-fire castle.” Before her death, Faye Goodwin mentioned a dragon who lived near the loch. Hoping to find the long-lost dragon, Ilsa brings her daughters to the castle near Loch Ness.
Wren, middle child of Ram and Ilsa, has been afraid of deep water and the dangers that may lurk there ever since sinister creatures nearly drowned her in the Caspian Sea. But Ed, the mysterious porter at Nattertinny Castle, knows about deep lakes and the monsters that dwell in their fathomless depths. He promises to keep Wren safe from whatever attacked her under the water…but to what lengths must he go to keep his promise?

The Dragon Eye series books:
One: Dragon
Two: Hydra
Three: Phoenix
Four: Vixen
Five: Dracul
Six: Basilisk