This could be a tricky one.
The DUKW is a 70 year old piece of machinery- which will give rise to mechanical / engineering problems.
It is also an absolutely fantastic piece of engineering that cheaply solved a major logistic problem in WW2, and has been copied over time (e.g. Stalwart).
Is it a safe mode of water transport today? Well I was happy to take my family on it last year for a very different view of London, and the experience of driving in /out of the Thames as fantastic....although the lack of freeboard did give me a slight concern.
I think the solution is in proven maintenance -which my all my LGV vehicles have to go through and be 100% auditable. This is not cheap but is the price to pay for operating any vehicles - or boat - as I'm sure the trade members will agree is vital.
Let's not prejudge this - I would be very sorry to see the DUKW not live on in any guise through this incident. Will be interesting to see what MAIB make of this one.