My name is Bob, and I've got a soft spot for all action and adventure stories. I think you're off to decent, interesting beginning, but your prologue is all skeleton with no flesh on the bones, so to speak. Granted it's a short piece and you likely have more to add to this, allow me to help you along if I might. I've written and published six action/adventure fantasy novels, so you can understand my desire and enthusiasm with regard to what you appear to have in mind.
Right now, what you have would be about the minimum length for a prologue, and given what you have going, it is currently much too short -- or abbreviated, I suppose, would be a better description. You have the right idea in terms of a prologue setting the stage, and "hooking" a reader so that they can hardly wait to jump into chapter one. But prologues can be tricky, risky, and even dangerous to you, as the author. Dangerous with respect to losing readers before they even get started.
A prologue sets the stage in more ways than one. It tells us very quickly how good, average, or even poor a writer is, and what we, as readers, can expect in the pages that follow. If I were reading this as a potential novel, I'd soon be moving on to another, different book -- not because the writing here is so bad, but simply because it's sparse, empty, absent any particular shine or sparkle. I love the idea of the five gates and the characters' arrival at Forbidden Island. But the writing style itself is so devoid of the kind of details that make these stories come alive, that boredom threatens us far sooner than whatever -- or whoever -- lurks behind those gates.
So what kind of details am I referring to? Okay, that's the key question, isn't it? The answer has to do with the proposition that as soon as possible, the author must answer the following questions: Who, What, Where, How, When, and Why.
These are the big "six" that put the reader inside the helicopter, let him or her step out onto the ground (along with the rest of the crew), and then survey the immediate environs. We want to smell the odors that hang in the air, hear the sounds that emanate from what is likely a surrounding jungle, feel the humidity of the warm, summer heat, and watch as the sun sets low on the ocean horizon.
Based upon the skimpy pickings you've given us thus far, we know the Who, and a teeny bit about the What. All the rest is unknown. At the end of a good prologue, however, the only one of the six that is typically left out of the mix is the Why. That's what we're here to find out, right?
There's a number of small grammar and technical issues that also need to be addressed, but I don't want to do too much all at one time. Certainly not before you've had a chance to "juice" this up like I hope you're now inclined to do
In closing, keep in mind that the reason we love movies with these kind of themes, is precisely because five of the six items I list here, are not only answered, but done so with lots of music and other fanfare. Although you can't provide the music, you can offer your readers all the rest, and do it with style. So grab your dictionary and thesaurus, and start dog-earing those pages
Let me know if I've shaken the ground a bit, and if you have any questions. I'd also love to see a rewrite of this, if and when you do. Thanks for listening.