If you’ll be swimming in a pool just for fun, bring toys in your bag that you can use to entertain yourself. Dive toys are fun to use to practice swimming to the bottom of the pool, and they come in lots of different shapes and sizes.  Choose dive sticks that are shaped like thick markers with a weight that pulls them to the bottom of the pool. If you don’t want to buy dive toys, throw pennies into the bottom of the pool to try to retrieve. Make sure you’re allowed to use dive toys at the pool where you’re swimming. Reading is a great activity to do when you need a break from swimming. Pack a book or magazine in your bag to keep you entertained.  While hopefully it won’t happen, it’s possible that your books might get wet being next to the pool, so bring ones that you don’t mind getting splashed on a little. You might bring a journal and pen to write instead of reading. Attach the headphones to your phone or portable music player to listen to the music by yourself, or sync the music with portable speakers so everyone can hear music. Remember that you’ll be near water, so choose electronics that can withstand drops of water.  Bring headphones to listen to music while you lay by a public pool, or bring a small speaker to listen to music at the beach. Be aware of others around you and don’t play music loudly if you’re in a public place. This is a great thing to pack if you’re going to hang out at a friend’s pool. Bring a small float that will be easy to blow up, deflating it once you’re done to pack it back in your bag.  Some public pools don’t allow floats, so be sure to ask before bringing one. Floats can be dangerous to use in the ocean or lake if the water is rough, so use caution. If you’re at a long swim meet, you might want to bring a deck of cards or other small game to play while you’re waiting. If you’re spending time at the pool, you might bring pool toys, noodles, or fins. Find any other small activities you might like to do and pack them in your bag if desired.  Avoid bringing more than one or two...

TL;DR in Vietnamese:
Đồ chơi lặn dưới nước. Chọn một cuốn sách để đọc cạnh bể bơi, biển hoặc hồ. Mang theo tai nghe hoặc loa để nghe nhạc. Mang theo phao bơi để bám và thư giãn trên mặt nước. Mang theo trò chơi hoặc đồ chơi mà bạn thích. Xếp những đồ cần sử dụng trước lên trên.