Tremiti Islands?

I have considered it, or more so Gargano in general, but I never had time in my itinerary (on two ten-day visits to Puglia and Basilicata), so it really takes giving up something else and would depend on the overall itinerary. I think a day trip is pretty unlikely unless you are staying in/adjacent to one of the towns that has ferry access (check the schedules for September, too)
When looking for info on a place like the islands, in addition to posting on a forum, I search for blog posts--I often get good info that way. Also, European newspapers are often a great resource (see below). Good luck!
https://www.theguardian.com/travel/2019/apr/20/italy-tremiti-islands-you-wont-find-this-on-capri
https://nextstop-italy.com/islands/san-domino-breathtaking-views/

Thanks.

Absolutely, it's always true, if you choose to do this, you can't do that - the eternal choices and trade-offs of planning.

That said, we will have 19 full days in Puglia (not counting arrival/departure days) and while I realize one could easily spend months there, with 19 days to play with, the real question is, can we afford to spend a few of those days in Gargano (I'm considering Vieste and Isole Tremiti, about 2-3 days total between them). I think I can justify that and still reach most of the other places on my menu - but currently Tremiti is on the bubble, but I'm leaning towards it (feel free to dissuade me, folks). I think a long day-trip is do-able, but obviously would give us very limited time on the islands; an overnight would be more relaxed and I'm also considering that. We are snorkelers, and Tremiti looks like a great place for that.

Agree about seeking out multiple sources (I have). The linked Guardian article confirms a lot of what I've seen elsewhere (and checks all my boxes); I've seen some other references complaining about trash and a general run-down state of things (I actually like run-down, but trash not so much). As for blogs they can be helpful but I find most have a hidden (or not-so-hidden) agenda (selling me things) which makes me extremely wary to believe much of what they're saying/selling (just like so-called "social media" where it seems nearly everything posted is misleading to some degree). Not really any hidden agendas from folks here IME so that's why I floated the question.

There seems to be a rapid swelling (at least here) of interest in Puglia (which concerns me, so I'm hoping to beat the rush towards overtourism); Gargano doesn't seem to be getting the same degree of attention, which has some appeal, too. We'll see about all that.

Thanks for your insights.

If I had 19 days and was traveling in September, I would definitely work it in--I like outdoors things most of all, so easy decision!

I was at the Gargano last summer 2023 and wanted to go, but decided against it because I’m lazy and I had to get up too early to make the only hydrofoil departing at around 9am (passengers only, cars are not allowed). The return trip from the islands was at around 5pm or so. Friends of mine in Italy told me the islands are great for swimming and snorkeling, but there isn’t much else to do. I think it’s doable as a day trip. The main port to get there is from Termoli, which has year round ferries and hydrofoils, but in July there were also passenger only fast boats from Vieste, Peschici and Rodi Garganico. Probably they still have boats from those towns in September. From the Gargano there was only one run a day going and one coming back. The crossing was about 1.5 hour, so you could potentially be there by 10:30am. That would give you about 5-6 hours for a day sunbathing and swimming in one of the little coves walking distance from the harbor.

https://www.turistinpuglia.it/en/isole-tremiti-cosa-vedere-e-fare-in-un-giorno/

We spent a few days in Vieste last mid-September and loved the town, and had wonderful dinners both in town and in an agriturismo reachable by taxi or car. It is a gorgeous town and I would love to go back. It was not at all crowded in mid September. From there we drove to Termoli and onwards towards Rome.

I did not consider the islands due to scant ferries and lack of time. But the water off Vieste was warm enough to swim at that time but I did see a few jellyfish. We stayed in a great hotel long walking distance or short taxi or car drive to the town center; ample parking by the marina in September. Vieste is a beautiful, gleaming white town and the food is a bit different than further south in Puglia.

Be sure to check out the agriturismo I mentioned, which is part of a family multi-generational farm with lots of goats, both live and on the menu!!!!! If you need the name I will look it up and post.