Guiding Light

Tall and tough through tumultuous times.
Guiding light from dusk to dawn but
I am not the sky candle of the night.
The land of Poseidon may thrash against me
And grains of sand crushed under my weight.
Sheltering the lost and weary from the water's
Foamy flinging and forgotten phantoms who ignored my guidance.
The winds cannot kill the light I emit
Rather, the light prefers to dance back and forth by image reflectors.
So before my bowl of fireflies burn out by the morning
Tell me, what am I?