Just my tuppence worth and an excuse to talk about the amazing St Kilda trip!
We did the trip a few years back from Harris (Leverburgh), our second attempt as our first go, the trip was cancelled due to weather.Both times we booked with Sea Harris (with a slightly faster, newer boat) and they and the boat itself were first class.Super comfortable.
It’s a LONG , never to be forgotten day but you need 4days on Harris - the first day to actually be on the island as the next day, your first potential sailing day, leaves at 8am or thereabouts so you need to be on Harris (or Lewis) the night before. They will offer the next day as an alternative if the first day doesn’t run because of weather(mainly wind strength and direction.) Then as you return around 7pm you will most likely be on Harris/Lewis or one of the Outer Hebrides until the next day too.
It’s about 2.5 hrs out to St Kilda via a fairly fast boat.
My own experience with photos written up here, if of interest though there is tons online these days too.
https://annestravelsandhikes.com/2017/08/03/st-kilda-day-trip/
Just when you think you’ve seen some very dramatic (and of course fascinating) landscapes on Hirta the boat takes you out to Boreray and the sea stacks which offer the most astonishing coastal scenery I’ve yet witnessed, to me the highlight of the whole trip for wow factor.
It’s almost a Stone Age landscape out on Hirta in many ways with the surprisingly large stone cleats, used for storage, dotting the landscape above the bay in their hundreds.The finest book I’ve read on St Kilda is Charles Maclean’s -well worth doing some research before you go, as already suggested.
It is also a hostile living environment out on St Kilda, so remote too etc.There is a Gaelic saying, explained to me by my mother-in-law which translated into English as ‘I’d rather be on Hirta’ - said when anyone was faced with a particularly unpleasant task!