Plot hole: In the Ice Tunnel scene, Manny, Sid, and Diego come to a stop on the vertical block of ice. It breaks, and they slide through a 'field' of icicles sticking out of the ground. Their 'sled' is shaved down to nothing, indicating that the icicles are sharp. After going through the same tunnel as the baby, how did the baby make it through that field? (00:46:53)
Suggested correction: A possible reason for the sled slowing down is not due to the ice tunnel but the sheer several tons of weight the sled had on it while it was sliding through the tunnel.
Good point. Without the weight, the icicles would had slowed down the sled instead. And since the baby hardly weighs anything at all, it wouldn't have been able to slide through the field, it would've just collided with the front icicles and stayed there. But it still leads back to question of how the baby got through the field.
Not true, their "sled" is destroyed by the icicles.
Plot hole: During the nova scene, everyone is tying down the sails after securing themselves with lifelines to the mast. Jim and Silver are on the front and Silver is knocked off. Jim is then all dramatic and runs to grab Silver's lifeline which seems to be coming from above, and pulls Silver up like a pulley. How come? The lifelines were attached to the mast, so Jim's action is pointless... even if he could do it, because a shot later both lifelines are streaming right to the mast, leaving no room for a pulley of any sort.