Origin: other, https://github.com/frogatto/frogatto/issues/421#issuecomment-749181032
Author: Reiner Herrmann
Bug-Debian: https://bugs.debian.org/1010804

--- a/src/water.cpp
+++ b/src/water.cpp
@@ -165,8 +165,6 @@
 	if (glBlendEquationOES) {
 		glBlendEquationOES(GL_FUNC_REVERSE_SUBTRACT_OES);
 	}
-#elif defined(GL_OES_blend_subtract)
-	glBlendEquationOES(GL_FUNC_REVERSE_SUBTRACT_OES);
 #elif defined(USE_GLES2)
 	glBlendEquation(GL_FUNC_REVERSE_SUBTRACT);
 #else
@@ -212,8 +210,6 @@
 	if (glBlendEquationOES) {
 		glBlendEquationOES(GL_FUNC_ADD_OES);
 	}
-#elif defined(GL_OES_blend_subtract)
-	glBlendEquationOES(GL_FUNC_ADD_OES);
 #elif defined(USE_GLES2)
 	glBlendEquation(GL_FUNC_ADD);
 #else