What are some "essentials" that you'd recommend every Sailor having with them prior to deployment?

You squids need to belay that small boy term, it sounds rather perverted......................

I had reasons to not go Navy.. and read’g these comments I remember why I didn’t..
I went AF and deployed to some bard bones places .. I brought along a few books, Paperback of some novella that wound up being wipe paper.. at least pages were big enough and not waxed.. toilet was in a outhouse so no prob there..
no need for I pad(wtf was that? .. it’s ‘83)
Had a Walkman and plenty of batteries they almost didn’t let me bring from Germany.. I think I had 2 left(in the Walkman.. they made it all the way back to U.S. soil.. in the U.S. base in Germany was still German soil. Was in Sudan in K-Town there.. some Sudanese tried to sell me a empty shell of a 6 band radio.. nice try.. i’d Like to hear before buying.. oh.. very good radio, cannot let you listen..
Might wake child... only $10 American!
I passed on it... just glad that wasn’t a long deploy... glad to get home ! Did get to the coast... beach wasn’t clean.. lotta dead fish... so no swimming... musta been a red tide.. water oily.. took along kippers n crackers and decent dry stick salami.. that wasn’t greezy... got that in Germany.. had some good Lowenbrau
Wrapped and stored in a ammo can with a top secret tag ... had a bud at base command Post get the tag.. Customs guy wanted to look anyway.. the other Customs guy got me through.. so we enjoyed the Lowenbrau that first night .
It was Lowenbrau export.. I brought one empty bottle with cap back .. wrapped good.. so it didn’t break..
my brother not understand’g the meaning of the memory of it took it with some other bottles and took to work and had a place that took them... what a jerk! So much for them memories..

KY

I had to walk to work, I didn't have a ship to ride. I would tell a sailor he needs to know how to swim and tread water.

Bring the basics, toiletries, toilet paper, spare pair of glasses if you wear them, iPod/MP3 player, tablet or laptop, book,

Rx medications make sure that they are filled before you leave as sometimes the Medical Dept. Don't have them. Also get some motion sickness pills you can get them from Medical. A lot of people get sea sick I know I was a Corpsman.

Also do not bring a lot of food of any kind. You are not supposed to have any in berthing. It's yuck and attracts bugs. You will have the ships sore and geedunk machines aboard. Bring some cash and change, your debit card and a few checks. Sometimes you can cash a check if you need money. At least you could back in 2003 when I was on a ship.
Get a good note pad and some flash cards so you can study to get your qualifications done. Most of your free time will be spent studying until you get them done.

If your shop has room for a small Rubbermaid container and the people in your shop are cool with the arrangement, I recommend Tuna fish in the tearable packets. Peanut butter, and my personal favorite, Fluff. I always had a few dozen Ramen noodle packets as well. and a few small Tupperware bowls to make the ramen in on the mess decks.
I had CSER1 as my shop on both my DDG's so that was my setup. The Toilet paper, extra undies, and the other comments are spot on as well. I also remember watching movies on my iPod 160GB classic. At least now there are iPad pros and the like. I would definitely recommend digital media. Movies, anime, videos of loved ones. Music for working out, relaxing.

pack some extra shore line for sea anchors and some extra prop wash for keeping things clean and tidy

Take along a thick paperback or two that you thought you'd never find the time for ashore. Time between watches can become boring and having something to keep your mind on will add some value/enjoyment/escape to your waking hours.

Back when i served both in subs and carriers I always had 2 weeks of underwear,5-6 sets of working clothes (pooper suits in subs and dungarees in carriers) and at least 2 towels in my locker.

A camera. Don't let those memories escape. I was in 23 years. I've been retired 26 now. Still miss every it every day.