never touched a fone Diablo but maybe one problem is similar to my Ozone Chrono and a Pansh Kite I have seen these days.
Both have a, lets say "race orientated drainage" as maybe also the race kite Diablo could have. Or plain-spoken: just bad constructed drainage. If you are really just trying to win races, there is no need for a good drainage, as the race is already lost when the kite hits the water and there will always be a boat close which can pick you up.
But if you use a Foil kite for freestyle, freeride, freerace and especially like me crusing around lakes with very low and inconstant winds, the relaunching capability is pretty important for fun factor.
That's how the drainage of the last cell looks turned inside out of a Flysurfer Lotus 15 m² and every Flysurfer since 2004 in this size:
... and this is how it looks in my great (but not for difficult low wind) Ozone Chrono v1 15 m²(and also at Chrono v2 it is the same):
Even into the drainage of the tiny last cell of my Sonic 6 m² there are fitting 2 fingers comfortably.
So have a look what it is like on your Diablo. With some effort it can be possible to stamp one or two extra holes beside on the last 10 cells.
The rest is as said:
If the wind drops below 5 knts and stays there, better roll your foil up as long there is not too much water inside.
But if you do this well and you have a kite with a good constructed drainage, you may reassemble your foil again, when the wind picks up beyond 8 knts as shown here:
Hope this reduces some swimming with foil kites which is never necessary as long there is just a bit of wind.