My 2015 entry.
You play a professional salvage diver so experienced, the maneuvers become rote. Basically, as you go deeper into a dive, you sink further into cerebral journeys: childhood memories, revelations of horrors on land, hallucinations, philosophy of evil, the direction of art, and psychology of your crewmates. This permits some worldbuilding and characterization, though some readers may find the revelations interruptive.
I covered many themes, hopefully not too many: gradualism, freedom versus overregulation, the manchild generation, franchise over art, and rampant institutionalization. To balance the dreariness, we get some “cops and rubbers” and several comedic characters. All three endings have at least some happy element and scale depending on how well the player performed throughout the game. Success depends on choosing the logical underwater activities based on your chosen skill set. My main goals included depth, novelty, ease, likeable characters, replayability, and a new mechanic: the game somehow knows your path and all your encounters.
I included a similar mechanism in my 2013 entry, Gunlaw, whereby the game summarizes your journey no matter how twisted your path. Both methods involved something I call an eight-way split which I won't get into here. With Gunlaw, however, few readers would see the effect, or subending, because of the high difficulty of reaching it. In Frogmen, I darn well force players into the appropriate subending on every playthrough, no matter what. After writing three gamebooks with barely noticeable eight-way splits, I wanted this one blatant. Still, you'd have to play at least twice, taking different paths, to realize the game knows your every move. A first-time player could claim simple linearity as the reason for the game reporting his specific actions at the end.
High replayability of course means shorter playthroughs. I have other concerns as well. Hitting the competition's 25,000 word limit means the seabed gets scant description. Then again, the hero has seen it so often, he or she should have a nonchalant perspective. Star Wars fans may not appreciate their transformation from aficionados to brainwashed conformists in this future depiction where the masses swarm to the alpha franchises. It seems people have gone a little overboard with The Lord of the Rings too...
I pounded each line into its atomic letters. Regrettably, I had to remove too many he said's and she said's to tighten the word count. A good tip: before doing that, remove “turn to” before choices and just put the section number in parenthesis. This will free up hundreds of words. Also, you must research hyphenation. This will free up dozens of words too.
The writing lacks flow in places, but gamebooks can do that. On 63 and 65, I use gray. But on 33, I use grey. How embarrassing. Canadians like me often can't decide between the American system or the British one.
I learned to research heavily from this Matt Chat interview with Raymond Montgomery, the late CYOA author. I read articles and watched many diving and heist movies plus some episodes of The Beachcombers.
Hopefully, the high starting Air supply and uncertainty of how much you'll need in the final heist will create some tension. Players will always get a complete story, some strange treasure, character arcs, and four dives in diverse locations no matter how they play.
And a jig.