..as for the straps - there are some options starting from rubber lined leather straps to rubber straps to bmetal bracelet - but that's most likely no nnews to you.
As for overall "robustness" - IMO there is a lot of mythique, rumours and also misinterpretations out there.
Rolex, often quoted as the "arche type" of rugged sports watch - but one should consider the conditions for this "competition for the most rugged sports watch". For example, is it important
how the movemnet survives frequent downhill biking - or is it just important that it doesn't stop running at all?
Have a look at some Rolex movements frequently worn during likely activities - don't be surprised to see lot's of brasssing scratchmarks on plates/bridges caused by constant contact with the rotor. And same on the rotor itself and even visible in the inside of caseback. That's quite natural for automatic watches and not a big deal at all: the rotor is simply replaced duirng routine service and due to the fact that there is no display back, only the watchmaker will see the rest

Different story with PP here, the rotor of precious metal alone will add substantial costs when in need of replacement and there is a display back as well.....
Besides the fact that one would expect a llarger/thicker movement to be more robust compared to another one around 2mm slimmer,
it's more a question if one would be willing to explore the robustness of an Aquanaut - at heavy costs and considerable servive time -personally I wouldn't (but I wouldn't be surprised too much, if it wouldn't "stop" as well).
To be honest - I wouldn't even think of an automatic when asked for a mechanical watch to withstand something like downhill biking - I'd go handwound. Due to the nature of an automatic winding rotor - high mass, as few as possible fricton (likely delicate "mounting"), that's almost "worst case" for all heavy shoock/vibration duties.
All this no issue with handwound movements - the balance wheel area is the only shock sensitive part and sufficiently guarded by the typical shock protections.
How about something like a handwound Grand Seiko? I'm not sure about water resistance, but you'd have a real manufacture piece, beautifully finished case, dial and metal bracelets.
Best regards
Suitbert