Possible cause of the error failed returncode 20:
Happy New Year Virus
In the past, some players have reported problems with the game not working. After investigation, it turned out that the cause was a variant of the Happy New Year (HNY) virus.
If your system does not have antivirus protection, it is strongly recommended to download
VirusZ III from the official website and
perform a full system scan.

If HNY is found, be aware that
cleaning infected files doesn’t always work, because the virus can permanently damage executables. The file ‘aqb’, which is the main Aquabyss executable, might be cleaned, but it still won’t run properly afterwards.
If this happens, you will need to
reinstall the game using a clean installer downloaded from the store or FTP. Alternatively, if you do not have Internet access, unpack the game again from a complete archive.
xadmaster.library

Unpacking the game packed with
Lha with anything other than the latest
Lha 2.15 may end up with the game files corrupted (especially when using
xadmaster.library).
Please, use the latest version of Lha from Aminet: lha_68k
Alternatively,
LZX archive is also available. Both packs have the same content, there is no difference, and both can be downloaded from our
FTP and
Shop (
DE or
EN).
HDToolBox - MaxTransfer

For
CF/SD cards, setting
MaxTransfer too high may corrupt files. Documentation for PFS3 recommends
0x1fe00 (130 K) or even
0xfe00 (65024 bytes [
aligned to 512-byte disk sectors]) "if files greater than 64K get corrupted".
MaxTransfer tells the file system the
maximum block size it should request in a single disk I/O operation. If the value is too high, the system may try to read/write chunks larger than the controller or file system can handle, leading to corrupted files.
Because
MaxTransfer is a low-level disk/driver parameter, the information above applies to
all Amiga filesystems.