diff --git a/src/decomp/engine/surface_collision.c b/src/decomp/engine/surface_collision.c
index d788c60..7a8b15e 100644
--- a/src/decomp/engine/surface_collision.c
+++ b/src/decomp/engine/surface_collision.c
@@ -19,10 +19,12 @@ static struct Surface *find_ceil_from_list( s32 x, s32 y, s32 z, f32 *pheight) {
     for( int j = 0; j < surfCount; ++j ) {
         surf = loaded_surface_iter_get_at_index( i, j );
 
+        // libsm64: Weed out surfaces whose triangles are actually line segs. TODO do this at surface load time
+        if( !surf->isValid ) continue;
+
         // Do the check normally done in add_surface_to_cell
         if( surf->normal.y >= -0.01f ) continue;
 
-
         x1 = surf->vertex1[0];
         z1 = surf->vertex1[2];
         z2 = surf->vertex2[2];
@@ -93,6 +95,9 @@ static struct Surface *find_floor_from_list( s32 x, s32 y, s32 z, f32 *pheight)
     for( int j = 0; j < surfCount; ++j ) {
         surf = loaded_surface_iter_get_at_index( i, j );
 
+        // libsm64: Weed out surfaces whose triangles are actually line segs. TODO do this at surface load time
+        if( !surf->isValid ) continue;
+
         // Do the check normally done in add_surface_to_cell
         if( surf->normal.y <= 0.01f ) continue;
 
@@ -166,8 +171,12 @@ static s32 find_wall_collisions_from_list( struct WallCollisionData *data) {
     for( int j = 0; j < surfCount; ++j ) {
         surf = loaded_surface_iter_get_at_index( i, j );
 
+        // libsm64: Weed out surfaces whose triangles are actually line segs. TODO do this at surface load time
+        if( !surf->isValid ) continue;
+
         // Do the check normally done in add_surface_to_cell
         if( surf->normal.y < -0.01f || surf->normal.y > 0.01f ) continue;
+
         if( surf->normal.x < -0.707f || surf->normal.x > 0.707f ) {
             surf->flags |= SURFACE_FLAG_X_PROJECTION;
         }
@@ -285,17 +294,17 @@ s32 f32_find_wall_collision(f32 *xPtr, f32 *yPtr, f32 *zPtr, f32 offsetY, f32 ra
 s32 find_wall_collisions(struct WallCollisionData *colData)
 {
     s32 numCollisions = 0;
-    s16 x = colData->x;
-    s16 z = colData->z;
-
     colData->numWalls = 0;
 
-    if (x <= -LEVEL_BOUNDARY_MAX || x >= LEVEL_BOUNDARY_MAX) {
-        return numCollisions;
-    }
-    if (z <= -LEVEL_BOUNDARY_MAX || z >= LEVEL_BOUNDARY_MAX) {
-        return numCollisions;
-    }
+    // libsm64: Don't care about level boundaries with 32-bit ints for vertex positions
+    // s16 x = colData->x;
+    // s16 z = colData->z;
+    // if (x <= -LEVEL_BOUNDARY_MAX || x >= LEVEL_BOUNDARY_MAX) {
+    //     return numCollisions;
+    // }
+    // if (z <= -LEVEL_BOUNDARY_MAX || z >= LEVEL_BOUNDARY_MAX) {
+    //     return numCollisions;
+    // }
 
     numCollisions += find_wall_collisions_from_list(colData);
     return numCollisions;
@@ -350,4 +359,4 @@ f32 find_water_level(f32 x, f32 z)
 f32 find_poison_gas_level(f32 x, f32 z)
 {
 	return -10000.0f;
-}
\ No newline at end of file
+}
diff --git a/src/decomp/game/mario_step.c b/src/decomp/game/mario_step.c
index d3e2d8a..bbee5d2 100644
--- a/src/decomp/game/mario_step.c
+++ b/src/decomp/game/mario_step.c
@@ -12,7 +12,7 @@ static s16 sMovingSandSpeeds[] = { 12, 8, 4, 0 };
 
 struct Surface gWaterSurfacePseudoFloor = {
     SURFACE_VERY_SLIPPERY, 0,    0,    0, 0, 0, { 0, 0, 0 }, { 0, 0, 0 }, { 0, 0, 0 },
-    { 0.0f, 1.0f, 0.0f },  0.0f, NULL,
+    { 0.0f, 1.0f, 0.0f },  0.0f, 0, NULL, 0
 };
 
 /**
diff --git a/src/decomp/include/types.h b/src/decomp/include/types.h
index 71686b2..eb008b0 100644
--- a/src/decomp/include/types.h
+++ b/src/decomp/include/types.h
@@ -241,23 +241,24 @@ struct Waypoint
 
 struct Surface
 {
-    /*0x00*/ s16 type;
-    /*0x02*/ s16 force;
-    /*0x04*/ s8 flags;
-    /*0x05*/ s8 room;
-    /*0x06*/ s16 lowerY;
-    /*0x08*/ s16 upperY;
-    /*0x0A*/ Vec3s vertex1;
-    /*0x10*/ Vec3s vertex2;
-    /*0x16*/ Vec3s vertex3;
-    /*0x1C*/ struct {
+    s16 type;
+    s16 force;
+    s8 flags;
+    s8 room;
+    s32 lowerY; // libsm64: 32 bit
+    s32 upperY; // libsm64: 32 bit
+    Vec3i vertex1; // libsm64: 32 bit
+    Vec3i vertex2; // libsm64: 32 bit
+    Vec3i vertex3; // libsm64: 32 bit
+    struct {
         f32 x;
         f32 y;
         f32 z;
     } normal;
-    /*0x28*/ f32 originOffset;
-//  /*0x2C*/ struct Object *object;
+    f32 originOffset;
+    //struct Object *object;
     
+    u8 isValid; // libsm64: added field
     struct SurfaceObjectTransform *transform; // libsm64: added field
     u16 terrain; // libsm64: added field
 };
@@ -333,7 +334,7 @@ struct MarioState
     /*0x6C*/ f32 ceilHeight;
     /*0x70*/ f32 floorHeight;
     /*0x74*/ s16 floorAngle;
-    /*0x76*/ s16 waterLevel;
+    /*0x76*/ s32 waterLevel; // libsm64: 32 bit (address offsets after this are wrong)
     /*0x78*/ struct Object *interactObj;
     /*0x7C*/ struct Object *heldObj;
     /*0x80*/ struct Object *usedObj;
diff --git a/src/load_surfaces.c b/src/load_surfaces.c
index 709ffb4..2bb9b72 100644
--- a/src/load_surfaces.c
+++ b/src/load_surfaces.c
@@ -156,8 +156,14 @@ static void engine_surface_from_lib_surface( struct Surface *surface, const stru
         maxY = y3;
     }
 
-    if (mag < 0.0001)
-        DEBUG_PRINT("ERROR: normal magnitude is very close to zero");
+    if (mag < 0.0001) {
+        DEBUG_PRINT("ERROR: normal magnitude is very close to zero:");
+        DEBUG_PRINT("v1 %i %i %i", x1, y1, z1 );
+        DEBUG_PRINT("v2 %i %i %i", x2, y2, z2 );
+        DEBUG_PRINT("v3 %i %i %i", x3, y3, z3 );
+        surface->isValid = 0;
+        return;
+    }
 
     mag = (f32)(1.0 / mag);
     nx *= mag;
@@ -198,6 +204,8 @@ static void engine_surface_from_lib_surface( struct Surface *surface, const stru
     } else {
         surface->force = 0;
     }
+
+    surface->isValid = 1;
 }
 
 uint32_t loaded_surface_iter_group_count( void )