Revealing mistake: Blanche, Dorothy and Rose that went on the boat with the 3 guys were stranded on what appears to be a beach. However, the "beach sand" has a lot of bouncyness to it. Giving the look of foam padding of some sort with some fabric that looks like sand. The sand doesn't actually move either while they're walking on it. (00:16:11 - 00:18:40)
Continuity mistake: When the girls are sitting around the campfire, the amount of burned wood changes from shot to shot. First it's partially scorched, then mostly scorched then partially scorched again.
Revealing mistake: The "sand" on the beach of the supposedly lonely island Blanche, Rose, Dorothy and the three men stranded on is one solid cloth made of a rubber-like material. It wobbles and bends whenever a character's feet are on-screen.
Answer: Ice makers were a new invention, advertisement purposes.