World Generation

Ores automatically receive submerged variants generated by the mod; vanilla ores are verified to work, and most other ores should function as well. Patches will generate in their regular positions, but after generation, the portion of the patch which is underwater will be converted to use this submerged variant.

Submerged ores cannot be brought to the surface by landfilling; land-based mining drills can use the edge of their mining area to tap into submerged ores, but it's much more effective to use seafloor drills.

Fluid resources will generate as their regular variant on the surface of the water, and floating crude oil can combine nicely with adjusted refined concrete to make impromptu "oil rigs". Cargo Ships should consolidate to deep oil as usual if it's installed.

New Hardware

Wire Buoy

A floating counterpart to electric poles, the Wire Buoy closely resembles a medium electric pole, but takes up a 2x2 space, with a proportionally larger area (8x8 coverage). Can't be placed on land.

Floating Inserters

When combined with a new crafting item called the flotation platform, every variety of inserter can be changed into a variant you can place on water. The mod automatically scans for inserters and attempts to generate their floating variant; non-vanilla inserters should work, but there may be edge cases that haven't been accounted for (please feel free to file a bug report in that case).

Belts and Mining

Flotation platforms can also be used to create floating belts and seafloor drills. For the moment, these are functionally (and in the latter case visually) identical to standard transport belts and electric mining drills respectively. Drill spriting is hard.

Illumination

To keep your aquatic operations well-lit, the light buoy is also available, crafted with a lamp and some pipe. Like its terra firma counterpart, circuit integration is supported.

Other Alterations

Refined Concrete Fill

Refined concrete is now a more flexible landfill counterpart, and can be placed on (and removed from!) water tiles. It can't be removed when other entities on the tile would collide with the water it leaves behind, and other tile types (stone brick, concrete) can't be placed onto it.

By default, the mod reduces the yield of the refined concrete recipe from 10 items to 4; you can tune this anywhere from 1 to 10, or stop the mod from affecting the yield at all by setting the value to 0.

Fishing Calibration

Inserter fishing has been limited to only work with inserters capable of filtering. This can be disabled in settings, and disables the similar, more restrictive adjustment in Cargo Ships.

What It's Not

Water vehicles and long-distance logistics aren't within Dredgeworks' scope; see Dredgepack for my recommendations on accompanying mods. If there's something besides those that you think would be a good fit here, feel free to chime in.