I did my speedrun for Nancy Drew: Creature of Kapu Cave:
I got tripped up on fishing, and I ended up having to fish three times! Ugh. Someone could easily beat my record by doing everything the same way I did, but by having better luck on the fishing challenge. That happens with speedruns sometimes. If the random number generator is not your friend, the run can die quickly.
I went back on my own time and checked how fishing works. If you save and reload constantly, you can totally get 31 Big Island Bucks, the first time you go fishing. It takes a LONG time, but it works. Sometimes the game will try to force you to get an Ulua fish, but you can escape this trap by casting out the line, then immediately pulling it in. This resets the possible fish you can catch, for whatever reason.
I'm going to try a senior mode speedrun which is segmented, just to show what an optimized run might look like.