Avoid swimming alone, and stick to guarded beaches. Additionally, go swimming in the water in front of a lifeguard stand, especially if there are any alerts about possible rip currents or other hazardous conditions.  Swim near a lifeguard stand, but remember not to set up your blanket or chairs in front of the stand. The lifeguard will need a clear path to the water if they have to make a rescue. If you do go swimming on an unguarded beach, avoid going in deeper than your waist. It's also best to bring a floatation device into the water with you. When you get to the beach, look for flags or signs that indicate potentially dangerous ocean conditions. If you see a flag and aren’t sure what it means, ask a lifeguard. If you live in the United States, check your local beach forecast at https://www.weather.gov/safety/ripcurrent-forecasts. While strong winds can make waves choppier, rip currents aren’t directly caused by the weather and can form even in calm conditions. Key factors include the shape of the ocean bottom, sandbars, and structures such as jetties, rocks, and piers. Rip currents can form at any time, but they’re more likely to develop at low tide. Only a lifeguard or other trained emergency responder should attempt a rescue. If there is no lifeguard present, call emergency services and yell out instructions to the person caught in the current.  Yell to them “Stay calm! Don’t try to fight the current. Swim parallel to shore to get out of it.” Try to find an object that floats and, if possible, throw it to the person caught in the current. If you don't have rescue equipment, such as a life jacket or ring buoy, a surfboard, boogie board, cooler, or foam noodle could work as improvised floatation devices.

How would you rephrase that briefly using Vietnamese?
Chỉ bơi khi có nhân viên cứu hộ đang làm nhiệm vụ. Kiểm tra dự báo thời tiết bờ biển trước khi xuống nước. Hãy cẩn thận, ngay cả khi trời đẹp. Đừng cố gắng cứu người đang bị cuốn vào dòng chảy xa bờ.