Judas Priest recorded a 15 minute song about the Loch Ness monster on their last disc called, appropriately enough "Loch Ness". The song itself isn't too spectacular, but dig the first three verses/Chorus:
Grey mist drifts upon the water
The mirrored surface moves
Awakened of this presence
Dispelling legends proof
A beastly head of onyx
With eyes set coals of fire
It's leathered hide
Glides glistening
Ascends the heathered briar
This legend lives through centuries
Evoking history's memories
Prevailing in eternities on and on and on
Lochness confess your terror of the deep
Lochness distress malingers what you keep
Lochness protects monstrosity
Lochness confess to me
How's that for epic? I guess the modern home of cryptozoological song would be the entire genre of Power Metal (when not crushed beneath the weight of Tolkein references).