No or wrong collision detection on bottoms of blocks when underwater

Collision detection appears to be missing or misplaced on the bottom of Stone, Dirt, and other solid blocks when the player is underwater. This allows the player to enter the block from below, activating "x-ray vision" in directions where there are adjacent solid blocks.

Update: The collision detection problem also appears to affect slabs, stairs, walls, fences, and transparent full-size blocks such as glass, glowstone, and redstone lamps. However, the x-ray effect seems to work only in full-size blocks other than glass.

Steps to reproduce:

1. Generate a Creative world using seed 305324302.
2. Open the world. You spawn in a jungle, near the edge of an ocean.
3. Fly to X=-240 Z=-64. You are above an underwater ravine.
4. Descend into the ravine, then find a stone or dirt projection above water.
5. Fly upward into the stone or dirt.

Expected results:
You collide with the block above you and are unable to go up farther.

Actual results:
Your head is able to enter the block. You can then see and move through adjacent solid blocks as if in spectator mode.