Screenshot

This mod adds a water-themed portable container with some unique properties, that doesn't supersede shulker boxes and is more balanced than the backpacks that many other mods add. I wanted something that encourages exploration and discourages rushing to the End just to get some more inventory space.

Design principles:

It should be obtainable prior to finishing the game
It should be rare and somewhat challenging to obtain (at least in early game)
It should be less useful than shulker boxes before those are obtained
It should still be useful after shulker boxes are obtained, complementing them

Which lead to the Amphitrite Coffer, a portable container with these features:
- Non-craftable, only spawns in Ocean Monuments, with some loot inside (at least 1 Heart of the Sea)
- Can't be opened if not waterlogged or charged
- Has 2 rows of slots instead of 3 (+ 1 special slot)
+/- Some items are converted when they're put inside (e.g. powdered concrete to concrete)
+ Can be charged to convert some common items into rarer ones (e.g. deepslate tiles to dark prismarine)
+ Shulkers can be placed inside of it (the only nesting combination allowed, can be disabled from the options)

Regular Conversions

You can bypass conversions by using a shulker box, as items inside of it aren't affected. Bundles also work if they're available.

These conversions also work with hoppers, but the coffer has to be waterlogged or charged to pull/push items from/to hoppers.

Install Roughly Enough Items to display the list of recipes.

Charging
Placing a Heart of the Sea in the appropriate slot consumes the item and gives the coffer a (configurable) charge of 12000. This remains stable as long as "charged conversions" (see below) aren't used, even after the coffer is picked up and placed again. Charged coffers can be opened outside of water and emit a light level of 15.

Charged Conversions

Again, you can bypass these conversions with shulkers or bundles.

Enchantments and the potion of water breathing cost a charge of 50, crying obsidian and sea lanterns cost 2 each, everything else costs 1.

Note that while the Respiration III (helmet), Depth Strider III (boots), Impaling V (trident) and Luck of the Sea III (fishing rod) enchantments can be added to items that have already been enchanted (as long as the item matches), Aqua Affinity is only added to unenchanted books, because not being able to put enchanted books without wasting charge would be quite annoying and in most cases you don't want that enchantment anyway, particularly if the book has enchantments for other items. You can change this behavior by adding a recipe for minecraft:enchanted_book through datapacks (the current one only applies to minecraft:book).

New item conversions of either type can be added through datapacks (see 1, 2, 3, 4, 5 for some examples).

Suggestions for new recipes are welcome, but they have to be water-related. Only 1:1 recipes are supported at the moment.

Fabric API and Cloth Config are required.

Please report issues at github.com/orlouge/amphitrite-coffer/issues.