i'm sure people have sent you the answer 293 times already too but just in case, the water texture is a default photo filter on the tumblr photo editor!
WE HAVE A PHOTO EDITOR?
Woagh
Not one person knows how tumblr works.
WE DO INDEED!!! :D
This is so beautiful to me
WAIT! I can make it worse!!
I can make it more worser!
Do you like the color of the photo editor?