There are two places in Ghosts of Saltmarsh where sinking is dealt with (in particular sinking from a hole in a ship take an hour from the primary example given)
In the adventure (designed for 4-6, 1st level characters):
The Sinister Secret of Saltmarsh
The section on
the Sea Ghost (in the sidebar)
[...] Holing Attempts to hole the ship and sink it requires the use of axes or similar implements applied with vigor. The undertaking takes 5 minutes [...]. If the hole is completed, the ship takes on water and sinks after an hour if the hole remains unrepaired.
This rule, taken in context, assumes that the party of characters in the adventure is taking part in this effort (ie 4-6, 1st level characters). If less characters were to attempt it the time taken should be appropriately extended.
This section is probably the most relevant section to your question as it specifically talks about creating a hole in the ship. 5 minutes of axing on a solid hull can create quite a sizable hole. This could easily be comparable in size to the hole created by the Disintegrate spell.
The other section that deals with sinking is in:
under the section on:
Death of The Emperor > Octopus Attacks > Sequence of Events > Rounds 3 through 20
the ship in this sequence is being actively attacked repeatedly by an enormous elder octopus intent on destroying the ship...