Mycelium spreads under seagrass

Steps to Reproduce:
1. Place mycelium near water
2. Place dirt under water close enough for mycelium to spread
3. Place sea grass on dirt
4. Wait for mycelium to spread

Observed Results:
Mycelium will spread onto nearby dirt blocks that are submerged and have sea grass above.

Expected Results:
Mycelium should not be able to spread onto dirt that is underwater