Diving gear doesn't change the result for heading towards the sound.
Fishing results. Still haven't found a water worm. Are they very rare or some limiting factor?
1 Fishing Modifier (heavy fishing pole)
Man, you didn't hook anything. Must be the weather or something. You've gotten better at fishing.
Man, you didn't hook anything. Must be the weather or something. You've gotten better at fishing.
You found: soaked newspaper You've gotten better at fishing.
You found: soaked newspaper You've gotten better at fishing. Your rank is now Learning.
Man, you didn't hook anything. Must be the weather or something. You've gotten better at fishing.
Man, you didn't hook anything. Must be the weather or something. You've gotten better at fishing.
Man, you didn't hook anything. Must be the weather or something. You've gotten better at fishing.
You found: soaked newspaper You've gotten better at fishing.
Man, you didn't hook anything. Must be the weather or something. You've gotten better at fishing. Your rank is now Amateur.
You found: fountain trout You found: deactivated ID You've gotten better at fishing.
You found: wormeaten mushroom You've gotten better at fishing.
You found: soaked newspaper You've gotten better at fishing.
You found: soaked newspaper You found: wormeaten mushroom You've gotten better at fishing.
Man, you didn't hook anything. Must be the weather or something. You've gotten better at fishing.
You found: fountain trout You've gotten better at fishing.
You found: 2 fountain trout You found: deactivated ID
You found: 2 soaked newspapers You've gotten better at fishing. Your rank is now Comfortable.
You found: soaked newspaper You've gotten better at fishing.
You found: deactivated ID You found: fountain trout
You found: soaked newspaper You've gotten better at fishing.
You found: deactivated ID You've gotten better at fishing.
You're starting to feel pretty comfortable with this whole fishing thing. You've learned a new Skill: Fishing You found: 2 soaked newspapers You found: deactivated ID
1 Fishing Modifier (heavy fishing pole)
Moderately Increased Fishing Yield (fishing skill)
You found: 2 deactivated IDs You found: wormeaten mushroom You found: fountain trout
You found: fountain trout
You found: washed coins You found: soaked newspaper You've gotten better at fishing.
You found: wormeaten mushroom You found: 2 soaked newspapers You found: deactivated ID
You found: washed coins You've gotten better at fishing.
You found: fountain trout You found: soaked newspaper
You found: deactivated ID You've gotten better at fishing.
You found: soaked newspaper You found: fountain trout You found: wormeaten mushroom You've gotten better at fishing.
You found: 2 fountain trout
You found: fountain trout You found: deactivated ID You found: soaked newspaper
You found: wormeaten mushroom You found: 2 fountain trout You've gotten better at fishing.
You found: fountain trout
You found: wormeaten mushroom You found: soaked newspaper You found: deactivated ID You've gotten better at fishing. Your rank is now Solid.
You found: soaked newspaper You found: mop You found: fountain trout
You found: wormeaten mushroom You've gotten better at fishing.
You found: 3 soaked newspapers You found: deactivated ID
You found: mop You found: fountain trout You've gotten better at fishing.
You found: fountain trout
7 Fishing Modifier
Moderately Increased Fishing Yield
Slightly Increased Chance of Fishing Up Actual Fish
Moderately Increased Chance of Deep Fishing
You found: soaked newspaper You found: deactivated ID You found: mop You found: fountain trout You found: water worm You've gotten better at fishing.
You found: wormeaten mushroom You found: fountain trout
You found: 4 fountain trout You found: soaked newspaper
You found: 3 fountain trout You found: washed coins
You found: soaked newspaper
You found: 4 fountain trout
Just looking at the number I had compared to other items from the fountain, even accounting for some crafting, it does seem like they might qualify as 'rare', but I don't know about 'very rare'. I've probably gotten 30-something of them over time.