Mod that reshapes Nauvis terrain and resource generation to be more ship-oriented:

map generation creates large continents – Encourages the use of both cargo ships and trains for logistics.
deep sea mechanic – You can't place landfill on deep sea tiles, which forces ship routes over ocean crossings (can be disabled in settings).
oil is only present in the Depths of Nauvis – By default, oil patches spawn only on water tiles, giving more reason to build offshore oil rigs (can be disabled in settings to allow spawning on both land and sea).
uranium is only present in the Depths of Nauvis – By default, uranium spawns only on water tiles. It is extracted as uranium sludge, which can be processed in a refinery into uranium ore (can be disabled in settings to allow spawning on both land and sea).

Depths of Nauvis