SHOOO BE DOO! https://www.youtube.com/watch?v=iakTl9SZTTY

src/main/java/com/minelittlepony/PonyRenderManager.java

@@ -47,7 +47,7 @@ public class PonyRenderManager {
     }
 
     private void addPlayerSkin(RenderManager manager, boolean slimArms, PlayerModels playerModel) {
-        RenderPonyPlayer renderer = new RenderPonyPlayer(manager, slimArms, playerModel.getModel(slimArms));
+        RenderPonyPlayer renderer = playerModel.createRenderer(manager, slimArms);
 
         ((MixinRenderManager)manager).getSkinMap().put(playerModel.getId(slimArms), renderer);
     }

src/main/java/com/minelittlepony/model/AbstractPonyModel.java

@@ -73,7 +73,7 @@ public abstract class AbstractPonyModel extends ModelPlayer implements IModel {
      * Checks flying and speed conditions and sets rainboom to true if we're a species with wings and is going faaast.
      */
     protected void checkRainboom(Entity entity, float swing) {
-        rainboom = canFly() && Math.sqrt(entity.motionX * entity.motionX + entity.motionZ * entity.motionZ) > 0.4F;
+        rainboom = isSwimming() || canFly() && Math.sqrt(entity.motionX * entity.motionX + entity.motionZ * entity.motionZ) > 0.4F;
     }
 
     public void updateLivingState(EntityLivingBase entity, Pony pony) {
@@ -222,7 +222,9 @@ public abstract class AbstractPonyModel extends ModelPlayer implements IModel {
     *
     */
     protected void rotateLegs(float move, float swing, float ticks, Entity entity) {
-        if (isFlying()) {
+        if (isSwimming()) {
+            rotateLegsSwimming(move, swing, ticks, entity);
+        } else if (isFlying()) {
             rotateLegsInFlight(move, swing, ticks, entity);
         } else {
             rotateLegsOnGround(move, swing, ticks, entity);
@@ -256,6 +258,43 @@ public abstract class AbstractPonyModel extends ModelPlayer implements IModel {
         bipedRightLeg.rotationPointZ = bipedLeftLeg.rotationPointZ = 10;
     }
 
+    /**
+     * Rotates legs in quopy fashion whilst swimming.
+     *
+     * @param move      Entity motion parameter - i.e. velocity in no specific direction used in bipeds to calculate step amount.
+     * @param swing     Degree to which each 'limb' swings.
+     * @param ticks     Total whole and partial ticks since the entity's existance. Used in animations together with {@code swing} and {@code move}.
+     * @param entity    The entity we're being called for.
+     *
+     */
+    protected void rotateLegsSwimming(float move, float swing, float ticks, Entity entity) {
+
+        float forward = ROTATE_270 - ROTATE_90/3;
+        float down = ROTATE_90;
+
+        float leftX = down + MathHelper.sin((move / 3) + 2*PI/3) / 2;
+        float leftY = -forward - MathHelper.sin((move / 3) + 2*PI/3);
+
+        float rightX = down + MathHelper.sin(move / 3) / 2;
+        float rightY = forward + MathHelper.sin(move / 3);
+
+
+        bipedLeftArm.rotateAngleX = leftX;
+        bipedLeftArm.rotateAngleY = leftY;
+
+        bipedRightArm.rotateAngleY = rightY;
+        bipedRightArm.rotateAngleX = rightX;
+
+
+
+        bipedLeftLeg.rotateAngleX = leftX;
+        bipedRightLeg.rotateAngleX = rightX;
+
+        bipedLeftLeg.rotateAngleY = 0;
+        bipedRightLeg.rotateAngleY = 0;
+
+
+    }
 
     /**
      * Rotates legs in quopy fashion whilst flying.

src/main/java/com/minelittlepony/model/player/PlayerModels.java

@@ -1,6 +1,11 @@
 package com.minelittlepony.model.player;
 
 import com.minelittlepony.model.PMAPI;
+import com.minelittlepony.render.player.RenderPonyPlayer;
+import com.minelittlepony.render.player.RenderSeaponyPlayer;
+
+import net.minecraft.client.renderer.entity.RenderManager;
+
 import com.minelittlepony.model.ModelWrapper;
 
 public enum PlayerModels {
@@ -12,7 +17,12 @@ public enum PlayerModels {
     PEGASUS("pegasus", "slimpegasus", () -> PMAPI.pegasus, () -> PMAPI.pegasusSmall),
     UNICORN("unicorn", "slimunicorn", () -> PMAPI.unicorn, () -> PMAPI.unicornSmall),
     ALICORN("alicorn", "slimalicorn", () -> PMAPI.alicorn, () -> PMAPI.alicornSmall),
-    ZEBRA("zebra", "slimzebra", () -> PMAPI.zebra, () -> PMAPI.zebraSmall);
+    ZEBRA("zebra", "slimzebra", () -> PMAPI.zebra, () -> PMAPI.zebraSmall),
+    SEAPONY("seapony", "slimseapony", () -> PMAPI.seapony, () -> PMAPI.seapony) {
+        public RenderPonyPlayer createRenderer(RenderManager manager, boolean slimArms) {
+            return new RenderSeaponyPlayer(manager, slimArms, PlayerModels.UNICORN.getModel(slimArms), getModel(slimArms));
+        }
+    };
 
     private final ModelResolver normal, slim;
 
@@ -34,6 +44,10 @@ public enum PlayerModels {
         return useSlimArms ? slimKey : normalKey;
     }
 
+    public RenderPonyPlayer createRenderer(RenderManager manager, boolean slimArms) {
+        return new RenderPonyPlayer(manager, slimArms, getModel(slimArms));
+    }
+
     /**
      * FIXME: PMAPI fields are null when the game starts.
      */

src/main/java/com/minelittlepony/model/ponies/ModelSeapony.java

@@ -92,8 +92,16 @@ public class ModelSeapony extends ModelUnicorn {
         bipedRightArm.rotateAngleY += 0.3F;
     }
 
+
+    @Override
+    protected void rotateLegsSwimming(float move, float swing, float ticks, Entity entity) {
+        super.rotateLegsOnGround(move, swing, ticks, entity);
+    }
+
     @Override
     public void render(Entity entity, float move, float swing, float ticks, float headYaw, float headPitch, float scale) {
+        setVisible(bipedLeftArmwear.showModel);
+
         GlStateManager.pushMatrix();
         GlStateManager.translate(0, 0.6F, 0);
         super.render(entity, move, swing, ticks, headYaw, headPitch, scale);

src/main/java/com/minelittlepony/pony/data/PonyData.java

@@ -72,7 +72,7 @@ public class PonyData implements IPonyData {
 
     @Override
     public boolean hasMagic() {
-        return race != null && race.hasHorn() && glowColor != 0;
+        return race != null && getRace().hasHorn() && getGlowColor() != 0;
     }
 
     @Override

src/main/java/com/minelittlepony/pony/data/PonyRace.java

@@ -13,7 +13,8 @@ public enum PonyRace implements ITriggerPixelMapped<PonyRace> {
     ZEBRA(0xd0cccf, PlayerModels.ZEBRA, false, false),
     REFORMED_CHANGELING(0xcaed5a, PlayerModels.ALICORN, true, true),
     GRIFFIN(0xae9145, PlayerModels.PEGASUS, true, false),
-    HIPPOGRIFF(0xd6ddac, PlayerModels.PEGASUS, true, false);
+    HIPPOGRIFF(0xd6ddac, PlayerModels.PEGASUS, true, false),
+    SEAPONY(0x333333, PlayerModels.SEAPONY, false, true);
 
     private boolean wings;
     private boolean horn;

src/main/java/com/minelittlepony/render/player/RenderPonyPlayer.java

@@ -93,8 +93,7 @@ public class RenderPonyPlayer extends RenderPlayer implements IRenderPony {
     public RenderPonyPlayer(RenderManager manager, boolean useSmallArms, ModelWrapper model) {
         super(manager, useSmallArms);
 
-        playerModel = model;
-        mainModel = ponyModel = playerModel.getBody();
+        setPonyModel(model);
 
         layerRenderers.clear();
         addLayers();
@@ -194,12 +193,14 @@ public class RenderPonyPlayer extends RenderPlayer implements IRenderPony {
 
         if (entity.isEntityAlive() && entity.isPlayerSleeping()) return null;
 
+        if (getModelWrapper().getBody().isSwimming()) {
+            return PonyPosture.SWIMMING;
+        }
+
         if (getModelWrapper().getBody().isGoingFast()) {
             return PonyPosture.FLIGHT;
         }
 
-        //TODO: MC1.13 transformSwimming()
-
         return PonyPosture.FALLING;
     }
 
@@ -219,9 +220,13 @@ public class RenderPonyPlayer extends RenderPlayer implements IRenderPony {
         mainModel = ponyModel = playerModel.getBody();
     }
 
-    protected void updateModel(AbstractClientPlayer player) {
+    protected void updatePony(AbstractClientPlayer player) {
         pony = MineLittlePony.getInstance().getManager().getPony(player);
-        playerModel.apply(pony.getMetadata());
+    }
+
+    protected void updateModel(AbstractClientPlayer player) {
+        updatePony(player);
+        getModelWrapper().apply(pony.getMetadata());
     }
 
     @Override

src/main/java/com/minelittlepony/render/player/RenderSeaponyPlayer.java

@@ -0,0 +1,28 @@
+package com.minelittlepony.render.player;
+
+import com.minelittlepony.model.ModelWrapper;
+
+import net.minecraft.client.entity.AbstractClientPlayer;
+import net.minecraft.client.renderer.entity.RenderManager;
+
+public class RenderSeaponyPlayer extends RenderPonyPlayer {
+
+    protected ModelWrapper seapony;
+    protected ModelWrapper normalPony;
+
+    public RenderSeaponyPlayer(RenderManager manager, boolean useSmallArms, ModelWrapper model, ModelWrapper alternate) {
+        super(manager, useSmallArms, model);
+
+        seapony = alternate;
+        normalPony = model;
+    }
+
+    protected void updatePony(AbstractClientPlayer player) {
+        super.updatePony(player);
+
+        boolean wet = pony.isFullySubmerged(player);
+
+        setPonyModel(wet ? seapony : normalPony);
+    }
+
+}

src/main/java/com/minelittlepony/transform/PonyPosture.java

@@ -7,6 +7,7 @@ import net.minecraft.entity.EntityLivingBase;
 public interface PonyPosture<T extends EntityLivingBase> {
     PonyPosture<EntityLivingBase> ELYTRA = new PostureElytra();
     PonyPosture<? extends EntityLivingBase> FLIGHT = new PostureFlight();
+    PonyPosture<? extends EntityLivingBase> SWIMMING = new PostureSwimming();
     PonyPosture<EntityLivingBase> FALLING = new PostureFalling();
 
     default boolean applies(EntityLivingBase entity) {

src/main/java/com/minelittlepony/transform/PostureFlight.java

@@ -14,7 +14,7 @@ public class PostureFlight implements PonyPosture<AbstractClientPlayer> {
         return entity instanceof AbstractClientPlayer;
     }
 
-    private double calculateRoll(AbstractClientPlayer player, double motionX, double motionY, double motionZ) {
+    protected double calculateRoll(AbstractClientPlayer player, double motionX, double motionY, double motionZ) {
 
         // since model roll should probably be calculated from model rotation rather than entity rotation...
         double roll = MathUtil.sensibleAngle(player.prevRenderYawOffset - player.renderYawOffset);
@@ -38,23 +38,22 @@ public class PostureFlight implements PonyPosture<AbstractClientPlayer> {
         return MathHelper.clamp(roll, -54, 54);
     }
 
-
-    @Override
-    public void transform(AbstractPonyModel model, AbstractClientPlayer player, double motionX, double motionY, double motionZ, float pitch, float yaw, float ticks) {
+    protected double calculateIncline(AbstractClientPlayer player, double motionX, double motionY, double motionZ) {
         double dist = Math.sqrt(motionX * motionX + motionZ * motionZ);
         double angle = Math.atan2(motionY, dist);
 
         if (!player.capabilities.isFlying) {
-            if (angle > 0) {
-                angle = 0;
-            } else {
-                angle /= 2;
-            }
+            angle /= 2;
         }
 
         angle = MathUtil.clampLimit(angle, Math.PI / 3);
 
-        model.motionPitch = (float) Math.toDegrees(angle);
+        return Math.toDegrees(angle);
+    }
+
+    @Override
+    public void transform(AbstractPonyModel model, AbstractClientPlayer player, double motionX, double motionY, double motionZ, float pitch, float yaw, float ticks) {
+        model.motionPitch = (float) calculateIncline(player, motionX, motionY, motionZ);
 
         GlStateManager.rotate(model.motionPitch, 1, 0, 0);
 

src/main/java/com/minelittlepony/transform/PostureSwimming.java

@@ -0,0 +1,20 @@
+package com.minelittlepony.transform;
+
+import net.minecraft.client.entity.AbstractClientPlayer;
+
+public class PostureSwimming extends PostureFlight {
+
+    @Override
+    protected double calculateRoll(AbstractClientPlayer player, double motionX, double motionY, double motionZ) {
+
+        motionX *= 2;
+        motionZ *= 2;
+
+        return super.calculateRoll(player, motionX, motionY, motionZ);
+    }
+
+    @Override
+    protected double calculateIncline(AbstractClientPlayer player, double motionX, double motionY, double motionZ) {
+        return super.calculateIncline(player, motionX, motionY, motionZ);
+    }
+}