I'll add the perspective of an employer to this.
While startups are generally casual (not even business casual), the line of how casual can you go really depends on the company. A polite question to ask your prospective employer would be "If you have casual dress code, do you mind sandals and shorts?".
I do think that is as crude as you should get.
And the answer for Orbius is YES! Shorts, T-shirts and Sandals are fine UNLESS You are meeting a client.
If you would get on a CROWDED bus (which you won't in a speedo swim trunk or a open belly tank top), it is generally acceptable.
Hopefully, this gives you some clue of How to ask. All companies are different. I haev worked at a company where the CEO PREFERS that no shorts or non-collared T-shirts be worn. Just have to respect his preference.
C.H.