What should I bring to a beach vacation?

UV proof t-shirt for midday swimming

Like a swimsuit but covers shoulders and arms. If you get sunburned easily, this can save your skin. Sunscreen works, but it's not perfect in the water. Most people don't use one, but then most people have unhealthy bright red sunburns

Surfing rashirs (rash vests) serve this function and are water suitable.
- Exactly. (Style varies a bit between hot and cold climates)
That is a really good idea! I think I may need to buy one once I'm out there

Umbrella (or shade structure)
Snorkel & mask
Beach Ball, Frisbee or paddle ball
Boogie board

I'm not going without a book/ereader.

And multiple cameras.

(Edit) particularly for the reader, I should mention "be careful of sand" and maybe have one of those little duster cans around to make sure the ports are clear. But it's too much of what I value in between soaking in the water to not bring.)

Do you have a good way to read without the screen being too dim / too bright? Oh maybe I'll need sunglasses
- I think they mean eink ebook reader, which would be fine in the bright sun.
On the mentioning of cameras if you're bringing an expensive one also bring a camera cleaning kit and a clean bag for your camera

Just to make sure you don't get sand in your camera

Sunburn relief cream, for when you screw up the sunblock application from not being used to being around the beach.

Pure (or as close to pure) Aloe vera is best if you can get
- I prefer a little lidocaine in mine but to each their own.

Trashbag, maybe not for what you bring but for the bits of crap you'll find scattered around the beach

That is a great idea! I hope there is not much trash but there always is some

Slippers.

Also put some ice on your water bottle; it'll keep your water cool.

Maybe not the pink bunny slippers though.
Better yet, get a thermos water bottle. Keeps water cold for up to 48hrs
~~Slippers~~

*thongs (flip flops / sandles for you non Australians)

Slippers are not suitable for the beach and would be ruined, once you get sand in them it's never coming out

I'd you're going to do some running on the beach bring running shoes that can be easily cleaned
Oh yeah good idea the sand is hot!

Flip flops or beach shoes, some kind of shade, and a HAT!

Not always necessary but can be nice: Bug repellent A cooler with water/ice Shoes/sandals/flip flops for walking in sand

Hat, maybe a fan if it's gonna be particularly hot

Also bring something to listen to, with headphones usually, but if you know that it won't annoy others, a Bluetooth speaker can be a good addition.

If you're gonna generate any rubbish, something to put that in and take it away again

I like to bring some cold beers too, but that's obviously not for everyone

I'm just seeing OP rocking up with a fan after reading your advice and wondering why there are no outlets on the beach
- I found a neat mister / spray bottle thing in my basement that would be nice, but i might not need it, I think there might be a breeze

A good book.

I was going to suggest The Hitchhiker's Guide to the Galaxy, after all, they will already have a towel.
- I could write 42 in the stand with a nice stick or a shell if I find one ;)

Coverup, rash guard, hat. I have to bring at least 2 of everything because wet clothes don't dry overnight here, ymmv. Goggles or snorkel if you like to look underwater. Clothes for going out to eat or bar. Hair ties, shampoo, conditioner, gel, because the beach wrecks my hair so bad, no cute beach waves here, just beach witch hair.

I get the wild hair too... I think I might bring a swim cap as well even though it looks a little dorky

I would defenetly bring multiple Towels, if you want to wash them between days.

And I love watershoes, you can use to swim, if you can afford them, it saves you from cutting your feet on sharp objects you perhaps oversee

Frisbee

A relaxed and open attitude. Then just enjoy.

A great big bottle of tap water or a gallon jug of water for when you're ready to leave. Why? So you can wash the sand/dirt off your feet before getting into your car.

Just leave it in the car and it'll be nice and warm when the time comes 👍

This was my sister's favorite suggestion by far, I'm definitely going to try this!

Spare change for ice cream

Something to scoop sand and something to put it into. Small shovel, small buckets.

Make sure the bag you bring this stuff in is a beach friendly bag that lets the sand fall out through loose knit threads, like a net. Also if you have clothes with pockets like that, bring them instead of clothes that have pockets made of tight knit cloth.

Also bring something to put seashells into for the trip back home. Maybe a plastic jar.

A bucket is always a good idea. You can find collapsible buckets that would be easy to fit inside a bag. Buckets are good for sandcastles and for bringing water to wash sand off of things.

I have a bag that used to hold basmati rice, and I kind of like it for a beach bag! I guess the sand does fall out!

Bring a diaper (nappy). When you go swimming, you can put valuables in the diaper (cellphone, jewelry, etc) and not worry that anyone will take it.

That's really clever, I love that! Someone stole my stuff from the beach onc while I took a nap, but they mostly got oranges and a swimsuit. Still, left a bad taste in my mouth
I put my stuff in a plastic bag, tie it up, bury it, and put some rocks in an innocuous pattern on top of it.

OP it could be helpful to add some context here as flying somewhere like Hawaii and driving an hour to a beach in NW Washington are going to have completely different recommendations.

Flying limits what you can bring and the climate of the beach you're traveling to can make a difference too. More northern areas aren't going to be as hot or dry so it might be advisable to bring a rain jacket or sweater and no swimming gear because the water is too cold.

Mid Atlantic beach, taking a car, but I'll be going with some other people so I probably just have room for motel stuff in one bag and beach stuff in the other

What beach? If you're going to one in California, bring a warm set of clothes. Even in the summer, it can be downright freezing. Last time I went down to Santa Cruz it was in the hundreds where I live but only 60f at the beach.

beer (cheaper away from the beach)
hat for shade
fishing pole if you like fishing
cheap old phone if you have one, can swap your sim card to it. Keeps sand and water away from nice newer phone

Snacks for energy and drinks for hydration under the sun.

You're gonna need something to that beer,wine and sandwiches cold. We got one of these Titan Wheeled Cooler. Sooo useful, and at the end of the day you can put all your shit in there to take back and dump responsibly. Costo had them on offer a while back or the usual online places.

i find chilling on inflatables with the waves relaxing so i would recommend an inflatable.

[water] bucket if you know the beach is known for fire pit gatherings. some people just bury their firepit in sand which tends to keep the sand warm longer than expected. water buckets are also nice if you want to find crabs hiding in sand.

vinegar, if the area is known for jellyfishes.

eyeglasses, mouth protection/ face mask if windy.

These are all great suggestions. I didn't know vinegar could work for jellyfish, that's awesome

e-ink reader
flip flops
cooler

Op are you male or female, because that would help people suggesting (for example female hygiene products)

electrolytes
not a thing to bring but let people know where you are going just in case you go missing
something to provide shade like a parasol or portable beach tent
toilet paper just incase the public bathrooms don't have them
waterproof bag for electronics
make sure you've got phone credit so you can call people for help if needed
whatever those chiller box things are called that can hold ice for a long time to keep drinks cold