Continuity mistake: When Robin is changing her clothes, after the scene in the water where "something swam up her shorts", she is actually changing out of the clothes she was wearing when the plane crashed, not the clothes she was wearing in the water.
Other mistake: When Quin is cutting the plane that's stuck in a tree, he uses a saw, that looks brand new. He's just been chased by pirates and jumped off a cliff - where did he get the saw from? Anything in the plane would be rusty by this point.
Plot hole: After running from the pirates, the two castaways almost stumble off a cliff. Unless they were running backwards, I'm sure they would have seen the cliff coming for a while, because when the camera zooms out you can see clear terrain for at least 20 metres until the edge of the cliff.
Factual error: When the aircraft crashes on the island, the front of the aircraft strikes the ground which would have bent the propeller. They would have never been able to fly it again with that prop.
Continuity mistake: When Frank is seated at the nightclub where Angelica performs, watch the light and flowers on the table. When he is seated the light is sitting in the center of a bunch of flowers. Next shot, the flowers are almost gone and the light has moved a good foot or so.
Factual error: Ford and Heche are supposedly on an island in the middle of nowhere, but in some shots you can see the tall buildings of a city off in the distance.
Continuity mistake: When Robin stumbles upon a wild pig, she is pretty close to wading in to the water in the lagoon. Yet in the next shot, she stumbles down a little hill for quite a way before she gets to the water.
Continuity mistake: When Angelica is doing her sexy dance for the tourists, her anklet changes legs between the close up shots of her feet and the far away shots of her.
Continuity mistake: When Quinn and Robin are flying off the island in the DeHavilland Beaver, after replacing the Wheels with Japanese WWII floats found on the island, you can clearly see the brace wires in between the floats. These wires shouldn't be there, since they used bamboo to attach and brace the floats.
Continuity mistake: When Robin and Quinn are standing on the cliff she is afraid to jump, he kisses her and in the shot facing him he has his hands on her face while he is kissing her, but in the reverse shot his hands are not on her face. He didn't have time to move them between shots.
Continuity mistake: Angelica and Frank get in a helicopter to join the search of Robin and Quinn. In the meantime, a day has passed on the island. We come back to Angelica & Frank who are in the helicopter wearing the same perfectly neat clothes as the prior day.