SWB (shallow water blackout) can work but can be a bit tricky to trigger if you're not used to swimming. It also leaves a pretty ugly corpse.
Jumping from a high place can be passed as an accident with a bit of imagination too. Like, going hiking in winter and falling "accidentally" off a cliff.
Any OD drugs can also work.
Off the top of my head, that's about it but be creative. Essentially any accidental death can be "helped" but it will rarely be very peaceful for both you and first responders.