Sea Serpent Storm Blue

is the Noble Phantasm of Caenis in their swimsuit. 
He throws himself forward while riding fast on the sea surface atop his water dragon. 
He fires his harpoon, and magical energy in the shape of a dragon wraps around the target and destroys them on a direct hit. 
When the True Name is released at the waterside, the offensive power is increased. 
Additionally, the harpoon he uses is a modified form of the "Trident of the Sea God" that he uses as a Noble Phantasm when he’s a Lancer. 
A glimpse of this can be seen in the appearance of his Third Ascension.Fate/Grand Order - Summer Caenis profile translated by Justiciar_Jyggalag at Reddit
==References==
Category:Noble Phantasms
Category:Anti-Unit Noble Phantasms
Category:B+ rank Noble Phantasms
Category:Noble Phantasms introduced in Fate/Grand Order
Category:Noble Phantasms of Caenis
Category:Snakes
Category:Dragons
Category:Mounts
Category:Swimsuit Noble Phantasms
Category:Aquatic animals