Foundation with Prismarine Variants
Use prismarine paving, 
chiseled prismarine, and prismarine brick blocks as your base. These blocks feel natural underwater and stack well together. Stained dark prismarine adds a moody, shadowy accent for pillars or accent walls.
Structural Elements
Build walls and details using prismarine stairs and slabs. These allow you to create sloped roofs, ledges, and layered designs that feel organic in water. Combine with quartz paving for contrast—the light quartz against dark prismarine creates elegant temple-like aesthetics.
Decorative Details
Add quartz brick and chiseled quartz variants for ornamental features. Use buttons and pressure plates sparingly as trim or ritual markers. The mod's expanded prismarine and quartz sets give underwater builds the architectural complexity usually reserved for land structures.