Seems similar to #301, but is occurring in version 1.16.5 on Antique atlas 5.4.4-forge. Exact same symptoms.
Map appears translucent over bodies of water or ice when shaders are enabled. I should mention that this can be reproduced using only optifine's internal shaders.

• Minecraft: 1.16.5
• Forge: 36.2.20
• AntiqueAtlas: 5.4.4-forge

no shaders

shaders

sorry if this has already been fixed; i wasn't smart enough to find a solution on the other bug pages :)

Duplicate of #301

Already fixed in 6.0.1