How to level up weapons?

[ricky.d.keim]

I've gotten some upgrades in the water but My Dart gun doesn't stay leveled up.

I've gotten it to level 3 before but it always returns to level 1 and it's pretty useless on the Bigger fish. like Tuna and Marlin and Sharks I can hit them with all 3 darts and they wont sleep so there's got to be something Im missing here.

why can't we just pay Weapon Weeb for upgrades or something?

[Honorable_D]

You need to use Duff. Using gun upgrade kits while out diving are only temporary.

[WhatEven]

As Cobra will tell you, anything that is gotten in the water will stay in the water, you only keep things you upgrade yourself. This means no matter what you always enter with a Lv. 1 of whatever weapon it is, but you can get permanent modifiers on land. I would recommend once you get the weapons shop app (since you have access to Marlin you should have it, top left of your phone and then click on the speech bubble over Duff) that you get one of the sleeper guns rather than the dart as I've found it to be unhelpful at catching the bigger fish you're after. Basic sleeper gun is a nice start as it has 8 shots and getting the parts for it isn't hard.

[RandomTurtle]

You unlock crafting weapons at one point in the story.

You unlock upgrading weapons a bit later in the story.

You unlock A 2nd round of upgrades much later in the story

[DFogz]

The upgrades you get in the water, and the upgrade you do out of the water are VERY different.

In-water upgrades will increase damage, increase the max number of fish the net can hold, or reduce the time it takes for sleep darts to take effect. They only last for that one dive, and they DO NOT upgrade your weapon to the next tier and let you catch bigger fish. That's out-of-water upgrades.
If you want to sleep/net bigger fish, you need bigger guns. More shop upgrades unlock later.