Still working on the problem of getting to Hydra from Athens airport on May 1, when ferry operators are on strike. The solution seems to be to get a car from Athens airport to Metochi and take a sea taxi or the Freedom I, II, or III to Hydra -- but I've been unable to verify that these services will be operating on May 1. Do sea taxis follow the lead of ferries and strike on May 1? or are they likely to be available?
This year in Greece, due to the Easter holidays, the public holiday of May 1st, Labor Day, will be postponed to May 7.
There is no information yet on what the ferry services will do, but it is likely that the usual strike will take place on May 7 instead of May 1 st.
https://greekcitytimes.com/2024/02/27/labour-day-to-be-postponed-until-may-7/
Ferries are selling tickets for May 8 but not for May 1. I think that at this point it would be difficult to switch dates since, presumably, there are ticketholders whose trips would have to be canceled.
There are private boats from Piraeus to Hydra. Google "private boat from Piraeus to Hydra" and you'll see options.
As far as I've heard the strike day is now May 7.
Have you seen this website?
It may be able to help with your questions:
We have already googled for private boats from Pireaus and found them too pricey for transfer of just two people. They'd be an okay value for a party of eight.