Super Mario World - speed of sprites underwater

Some sprites slowdown horizontally when they get into the water (e.g., shell, p-switch), even though the RAM address keeps the same value at frame boundaries (that we usually see).

original speed: effective speed
  0:   0
  1:   0
  2:   1
  3:   1
  4:   3
  5:   3
  6:   4
  7:   4
  8:   6
  9:   6
 10:   7
 11:   7
 12:   9
 13:   9
 14:  10
 15:  10
 16:  12
 17:  12
 18:  13
 19:  13
 20:  15
 21:  15
 22:  16
 23:  16
 24:  18
 25:  18
 26:  19
 27:  19
 28:  21
 29:  21
 30:  22
 31:  22
 32:  24
 33:  24
 34:  25
 35:  25
 36:  27
 37:  27
 38:  28
 39:  28
 40:  30
 41:  30
 42:  31
 43:  31
 44:  33
 45:  33
 46:  34
 47:  34
 48:  36
 49:  36
 50:  37
 51:  37
 52:  39
 53:  39
 54:  40
 55:  40
 56:  42
 57:  42
 58:  43
 59:  43
 60:  45
 61:  45
 62:  46
 63:  46
 64:  48
 65:  48
 66:  49
 67:  49
 68:  51
 69:  51
 70:  52
 71:  52
 72:  54
 73:  54
 74:  55
 75:  55
 76:  57
 77:  57
 78:  58
 79:  58
 80:  60
 81:  60
 82:  61
 83:  61
 84:  63
 85:  63
 86:  64
 87:  64
 88:  66
 89:  66
 90:  67
 91:  67
 92:  69
 93:  69
 94:  70
 95:  70
 96:  72
 97:  72
 98:  73
 99:  73
100:  75
101:  75
102:  76
103:  76
104:  78
105:  78
106:  79
107:  79
108:  81
109:  81
110:  82
111:  82
112:  84
113:  84
114:  85
115:  85
116:  87
117:  87
118:  88
119:  88
120:  90
121:  90
122:  91
123:  91
124:  93
125:  93
126:  94
127:  94
 -1:  -2
 -2:  -2
 -3:  -3
 -4:  -3
 -5:  -5
 -6:  -5
 -7:  -6
 -8:  -6
 -9:  -8
-10:  -8
-11:  -9
-12:  -9
-13: -11
-14: -11
-15: -12
-16: -12
-17: -14
-18: -14
-19: -15
-20: -15
-21: -17
-22: -17
-23: -18
-24: -18
-25: -20
-26: -20
-27: -21
-28: -21
-29: -23
-30: -23
-31: -24
-32: -24
-33: -26
-34: -26
-35: -27
-36: -27
-37: -29
-38: -29
-39: -30
-40: -30
-41: -32
-42: -32
-43: -33
-44: -33
-45: -35
-46: -35
-47: -36
-48: -36
-49: -38
-50: -38
-51: -39
-52: -39
-53: -41
-54: -41
-55: -42
-56: -42
-57: -44
-58: -44
-59: -45
-60: -45
-61: -47
-62: -47
-63: -48
-64: -48
-65: -50
-66: -50
-67: -51
-68: -51
-69: -53
-70: -53
-71: -54
-72: -54
-73: -56
-74: -56
-75: -57
-76: -57
-77: -59
-78: -59
-79: -60
-80: -60
-81: -62
-82: -62
-83: -63
-84: -63
-85: -65
-86: -65
-87: -66
-88: -66
-89: -68
-90: -68
-91: -69
-92: -69
-93: -71
-94: -71
-95: -72
-96: -72
-97: -74
-98: -74
-99: -75
-100: -75
-101: -77
-102: -77
-103: -78
-104: -78
-105: -80
-106: -80
-107: -81
-108: -81
-109: -83
-110: -83
-111: -84
-112: -84
-113: -86
-114: -86
-115: -87
-116: -87
-117: -89
-118: -89
-119: -90
-120: -90
-121: -92
-122: -92
-123: -93
-124: -93
-125: -95
-126: -95
-127: -96
-128: -96