Wow, you really are a professional game tester. I mean, if I were actively trying to find holes in the code I might do that but just as a regular player I doubt I would… admittedly it’s a lot easier today than 20 years ago thanks to proper multitasking!
And I thought I was bordering on the obsessive trying almost every object with the floorboard. (This could potentially be a spoiler even if you finished the game.) E.g., surprisingly the flagpole won’t open it. (This is only a spoiler if you haven’t finished Stonehenge.)
Oh, I figured it’d just be the blue crystal and that without the item mentioned you’d only float for five to ten minutes instead of “forever” (as far as gameplay purposes go).
I see! So the glitch is limited to the FM Towns version, it seems.
Another thing that’s interesting: after Zak’s demise, I checked on the others, and found that neither Melissa nor Leslie had lost any oxygen. Their helmets were both at forty-something minutes!