bedrock-samples/resource_pack/animations/pufferfish.animation.json

{
	"format_version" : "1.8.0",
	"animations" : {
		"animation.pufferfish.flop" : {
			"loop" : true,
			"bones" : {
				"body" : {
					"rotation" : [ 0.0, 0.0, "variable.zrot" ]
				},
				"tailfin" : {
					"rotation" : [ 0.0, "math.cos(variable.animationamountblend * 45.0) * -5.75", 0.0 ]
				}
			}
		},
		"animation.pufferfish.swim" : {
			"loop" : true,
			"bones" : {
				"tailfin" : {
					"rotation" : [ 0.0, "math.cos(variable.animationamountblend * 30.0) * -5.75", 0.0 ]
				}
			}
		}
	}
}