The bug: when TNT is dispensed from a dispenser and falls into water, then explodes in the water next to the player, the player takes zero damage (even at point-blank range, with no armor)

How to reproduce:
1. place a water source block on the ground
2. place a dispenser 2 blocks above the water, facing downward, with 1 block of air in between the water and the dispenser
3. add TNT to the dispenser
4. stand next to the water, and activate the dispenser using redstone to make it dispense TNT
5. the TNT should be dispensed into the air, and then fall down into the water while it is primed
6. stay next to the TNT and wait for it to explode

Other conditions that produce the bug:
-also occurs when TNT explodes in flowing water
-also occurs when several TNT blocks explode simultaneously in water
-bug was reproducible in multiple worlds/realms

(See attached video for example)