The biggest risk with having your eyes open underwater is the possibility of contamination. If the water seems especially murky or if it smells bad, consider keeping your head above water. Keep your eyes closed if you have to swim underwater in fresh water that is less than clean. Never swim underwater in sea water without goggles. The salt water of the ocean burns the cornea. Dip your head underwater and open your eyes. More than likely it won't be especially comfortable and your vision will most likely be very blurry. Some can see better underwater than others, but you'll probably only be able to make out rough shapes and shadows. Blink your eyes several times before coming back up above the water. Your vision will remain blurry, but if you continue to swim underwater with your eyes open for longer and longer the uncomfortable feeling should pass. Avoid touching your eyes while underwater so as not to push any particulate in the water onto your eye or under your eyelid. While not necessary, it's a good idea to rinse your eyes with clean water or saline after swimming without goggles. A good rinse should knock anything potentially harmful that might've gotten in your eye while swimming. If you wear contact lenses, it is advised that you never open your eyes underwater without goggles. The lens provides a place for debris to get stuck in your eye, risking harm. If you do swim with them, take them out and rinse both them and your eyes after the fact.

Summary: Make sure the water is safe. Test the water. Continue to acclimate your eyes. Rinse your eyes after you're out.

Finder allows you to access your user files and will open to the Documents folder by default. Click Applications in the left sidebar and scroll down to access the Utilities folder, which contains important system based applications, such as Keychain Access and Disk Utility. Terminal is an application that runs using the command line, similar to DOS. In the blank window that appears, type sudo nano /etc/hosts Press Enter. You'll be prompted to enter your administrator password, which is what you use to access your computer. Type it in and then press Enter. Open the hosts file. After pressing enter, a new window will open for you to edit. The hosts file is used to dictate how different web sites connect to your computer and save data. There will already be text within your host file. Do not delete or change this text. Underneath the text, there should be space for you to type. If there isn't already any space, click your mouse at the end of the last line of text and press Enter to create a new line to write on. 127.0.0.1 is your computer's local IP address. This is what web sites use to access your computer's files and save data. For example, if you wish to block Bing, type in www.bing.com. Typing in variations of websites will help ensure that they're blocked, like bing.com or m.bing.com Since the hosts file opens in a special window, you'll be unable to save normally. If, when you save, your file name ends with "-original", delete that ending. You can also click Save to exit. Click the red circle in the top left corner of the window to close out of the text editor and return to the Terminal's interface. While the Terminal window is still open, type the new command into the new command line. This will commit the changes to your computer and also formally close the special text editor. Test the websites you've blocked. If successful, your computer will be unable to connect to the website.

Summary: Open Finder. Open your Utilities folder. Double-click on Terminal. Access the hosts file. Enter your administrator password. Scroll to the end of the text file. Type "127.0.0.1" and press the spacebar. Type the website you wish to block. Press Control-O to open the save box. Press Enter close the dialogue box. Exit the editor. Type sudo dscacheutil -flushcache. Press Enter. Finished!

For example, if the total is $6, a customer might hand you $11 so that she can get back a single five dollar bill. On the other hand, if she handed you $10, she would have gotten back 4 one dollar bills. Especially for transaction not involving coins, it is usually simple to just count up. For example, if the customer bought a $42 hat and gave you $47, you would count: 1 five dollar bill ("You gave me 42, plus 5 makes 47.") It may not be immediately obvious how to get from $12.78 to $23.03. Here is where a little initial subtraction can simplify things: Start with the amount paid. Subtract from it to get a simpler number. In this case, 23.03 .03 = $23.00. Now subtract the same amount from the price: 12.78 .03 = $12.75. It's clear now that you'll need to first give back a quarter. 1 quarter takes you from $12.78 to $13.03. ("that's $13.03") 1 ten dollar bill ("plus 10 equals 23.03") As another example of a more complex situation, imagine that you're a waiter and a customer is purchasing a meal worth $112.31. They give you 6 twenties, a nickel, and a penny. Add the amount paid by counting up as you put the money down: 20, 40, 60, 80, 100, 120 and six cents. Tell the customer the amount paid: "$120.06". The customer gave you a bizarre amount of change, so this might be a good time to do a bit of subtraction. 120.06 - .06 = $120.00, and 112.31 - .06 = $112.25. Better. You need 3 quarters. Now start adding up from $112.31 to $120.06. 3 quarters ("takes us to 113.06") - We know this works from our earlier subtraction exercise. 2 one dollar bills ("114, 115") 1 five dollar bill ("and 5 is 120.06") Check your work: You gave .25 + .25 + .25 + 1 + 1 + 5 = $7.75. $7.75 + $112.31 = $120.06 the amount the customer paid.

Summary: Be prepared for customers to give you odd amounts in order to get back less change or certain denominations. Count up as you did before for simpler transactions. Consider doing a bit of subtraction first to make things simpler when dealing with more complex transactions. Give correct change confidently for any combination.

It's the green icon with a white phone and chat bubble. You'll find it either on your home screen or in the app drawer. It's the green circle with a white chat message at the bottom-right corner of the screen. It's the plus (+) next to the silhouette of a person's head and shoulders. You'll find it at the top of the screen. This is where WhatsApp will save your new contact. You can choose to save it to your device's internal storage or your SIM card. Start by typing the "+" symbol, followed by the country code (e.g. 44 for UK). For example, a UK phone number would look something like this: +447981555555. It's at the top-left corner of the screen. It's at the top-right corner of the screen. Your contact is now added, and your contact list is up to date.
Summary: Open WhatsApp. Tap the new chat icon. Tap the new contact icon. Select a storage location. Type a name for the contact. Enter the contact's international phone number. Tap Done. Tap the back button until you've returned to the new chat. Tap . Tap Refresh.