When the water is placed right under the block and when a player swims upwards and pushes against an upper block up the water the player can see through blocks. Below are attachments how it looks, and how to do this.
MCPE-37027
Seeing through blocks
Resolved
Fixed
0
(Unassigned)
136617
Confirmed
Windows
Windows 10
1.7.0.2 Beta, 1.7.0.9 Beta
1.8.0.8 Beta
Retrieved
Can confirm for 1.7.0.9 Beta, this also affects lava.
Relates to MCPE-33575.