It was very beautiful. But a little unlikely that they carried all those votives down there. Nonetheless, you can guess what it meant for Baines to follow in Ada's footsteps. He is putting it together that the piano means everything to her. Maybe the Seahorse is just a representation of Joy? Light? That the piano leaves something beautiful in it's wake? Is there any typical attribute associated with seahorses??
shareThe shape of the seahorse resembles a treble clef.
Parts of the film has an underwater theme such as the blue tint and there is an aerial shot that looks like as if it is underwater. I think the seahorse is just another thing that goes with this theme. This underwater theme is foreshadowing the final scene.
I think it is important to notice that Flora follows Ada and her path creates a Y. The later scene where Flora betrays Ada the Y path is used again.
At first I was trying to think of how the seahorse is in nature, where the male seahorse gives birth and the parental roles are reversed in this instance. I'm not certain that parental role reversal can be said in this film.
Two gender role reversals that I noticed. One is a man wearing Ada's wedding dress before the wedding photo.
And the other is SPOILER Alert: male castration symbolism of Ada getting her finger cut off.