Assuming these are correct, I would welcome help with the parsing....
12a. All that is found in unopened grave (8) - EVERYONE?(All)
17a. Was bather panicking at first in flood? (5) - SWAMP (Flood)
I see the P from P(anicking) - but that leaves SWAM for 'Was bather', which doesn't seem right.
3d. Nasty people to be arranged, poorly dressed? (7) - RATBAGS (Nasty people)