EDIT 14/09/2018: I definitely think this is caused by mining fatigue while trying to dig underwater.
the crash always occurs for me underwater whilst digging ocean monument blocks with mining fatigue curse from a elder guardian while crouched.

efficiency 1 diamond pickaxe, and a respiration 2 helmet without aqua infinity.
------------------------------------------------------------------------------------------------------ OLD REPORT
crouching while standing in a magma column and trying to break the block below you results in a crash.