Of the most dangerous apex predators of Equestria that prey on Sirens, the one that places second on the list is the Sea Dragon or the Blue Dragon. Normally a hunter of whales, porpoises, seals, and large fish these oceanic dragons have a fond sweet tooth for siren flesh and their gemstones. They usually fly high in the skies to locate a siren pod and track its movements for the weakest of their kind which usually is a mother and her pup. With specially designed wings which minimize sound signature in the air, the only warning sirens get is the off chance the sun happens to caste a shadow for a brief moment.
Using its sheer size the dragon slams into the shoreline in a shock and awe move to disrupt siron retaliation for just enough time to snag what it hungers for. Usually it gets what it wants and scoops up the unfortunate victims in one snap of its bone crunching jaws. There are occasions a siron is quick enough to intervene and either sacrifice himself or gain the upper hand and the pack drives the beast off. Though for the most part, a Sea Dragon never gives up on its hunt and tends to be one of the controlling factors to the siren's immortality and their populations.