Answers:
1. transparent
2. dire
3. estuary?
4. crustacean
5. lurking
6. nematocysts
7. douse
8. skulk?
Step-by-step explanation:
1. If windows aren't clean, they aren't transparent. Other options don't make sense.
2. We need a synonym of bad or horrible, dire is the best fit
4. Crabs are crustaceans
5. We need a synonym of hiding, lurking is it.
7. Cover or drench. Closest word is douse.
I'm always happy to help :)