Found sword - Disappeared

[Mazhron]

Not sure if this is a feature or what, but I found a sword from a yellow chest in the water. When I got to the surface and dived again, I had a knife. Any idea why my sword disappeared?

[ska.one]

That's how the game works, and Cobra will remind you of that (especially early on) if you talk to him. None of the melee weapons are available to start a new dive. Once you surface the melee weapon always reverts back to your diving knife. Same with any ranged weapons you find during a dive, but there's something you'll be able to do about that as you progress.

[Zades]

It's part of the roguelike element of the game. You only get your basic equipment at the start of each run, and you have to make the most of what you find. But that will change somewhat the further you get into the game as you unlock new features.

[Dark]

Reject Sword. Embrace Squeaky Hammer.

[uwurawr]

you pick up melee weapons in the ocean. You pick up guns as well. Guns turn into blueprints that can be used to craft a permanent option. Not sure if that's the same for melee.