A continuously updated list of "must-have" and "nice-to-have" gadgets to keep your pack small.
Water-Proof Electronics Bag
Let's start with the basics... protecting your most precious items..
I keep my electronics in a 13L Sea-To-Summit Dry-Sack; it gives me peace of mind, helps keep things organized and comes in handy for any planned or unplanned water-based activities. Note the optional sizes; I use the 13L bag because it fits my laptop, but there are multiple options, depending on needs.
Check out my post Choosing a Backpack for more detail and recs.
Go Pro // Underwater Camera
You have a few options if you're looking to record your underwater adventures, you can opt for a waterproof phone case, a waterproof camera, or go the classic GoPro route; of course, GoPro is the de facto standard when it comes to action cameras, but there are less expensive alternatives if you're willing to take the chance; the GoPro Hero 10 is the latest model (as of July, 2022).
I won't make any specific recommendations around waterproof phone cases, as there are hundreds of options on Amazon; just make sure it's IPX8 certified (waterproof up to 100ft/30m).
Powered 4-Port USB Splitter
If you're traveling with a laptop, or if you want to charge multiple toys at once, a 4-port USB splitter takes up very little space and comes in very handy; please note that most splitters are not powered, so if you need more than just laptop connectivity (for your mouse, keyboard, etc.), be sure whatever you buy specifies powered ports.
And if you really need to up your game, the Anker 565 11-in-1 Splitter adds HDMI/DisplayPort, USB-C, SD/MicroSD Card, Ethernet, and Audio ports, while still charging your devices.
Travel-Sized Power Strip
Depending on how much stuff you're trying to power, you may need or want a standard outlet power strip, many (or rather, most) hostels have limited outlets in hard to reach places, so make sure whatever you buy has a flexible cable; check out the NTOP Travel Power Strip for a starting point.
Wireless Bluetooth Sleep Masks
Sleep masks are a godsend when you're sharing a room with strangers, and I highly recommend keeping one in your pack; the one I'm currently using is this LC-dolida, or search "wireless Bluetooth sleep masks" on Amazon.
I'm sure you already have headphones, they're cheap and available everywhere, but I didn't want to assumptively leave them off the list.. search "in-ear wireless headphones" on Amazon.
Foldable Phone Stand
There are a bunch of options for foldable phone stands, and they are extremely useful; for an inexpensive option, check out the iMangoo kickstand; or for a more durable, flexible and long-lasting option, the Pocket Tripod Pro; or search "minimalist folding phone stand" on Amazon.
This low-profile, magnetic Speedy Mag Wireless Charger looks useful and promising, but I can't seem to find the specs or charge capacity, so check it out at your own risk!
Nomad Base Station Pro.. if you have lots of toys that need charging.
Lightening Charger + Multi-Port Cable
This is an absolute must-have when you're always on the move, you can charge your phone from dead to 100% in about 45 minutes, coupled with a multi-port cable, you can recharge all your devices while you wait for the hostel bar crawl host to arrive.
There are many options, such as a dual port (20W usb and usb-c ports), a multi-port (100W usb and multiple usb-c ports), or the original Anker USB-C single-port (20W usb-c port); just be sure they provide 20Watts of power (per port) and that you have the proper cables to power your devices!
Note: This post is under construction, check back later for more recs and tech!