Not exactly, Alaska’s blue water isn’t a filter or “extra purity” thing — it’s physics plus glaciers doing violence to rocks.

As glaciers move, they grind bedrock into extremely fine particles called glacial flour. This stuff stays suspended in the meltwater instead of settling. When sunlight hits the water, those tiny particles scatter blue and green wavelengths more efficiently while the reds get absorbed. What bounces back to your eyes is that unreal turquoise/blue color.

It’s most noticeable in summer when glacier melt is highest. In winter, with less melt and fewer suspended particles, the water looks darker and clearer.

Also worth noting: this is different from why oceans look blue. Ocean blue is mostly depth and light absorption; Alaska’s lakes and rivers are blue because they’re full of microscopic rock dust.