SportDOG FieldTrainer 425X is a highly rated E-collar system for dog training or hunting. The E-collar fits dogs 8 pounds and up, and it is also claimed to be waterproof for and submersible to 25 feet.
I have an older version SD 425 for a few years and it is quite reliable. It has seven static stimulation levels, plus a vibration and a beep function. It is claimed to have 500 yards of range, but I never tested that far. I use it mostly for my dog wandering in my yard as a moving invisible fence, and when she is too close to the boundary, I just press one button on the transmitter and the E-collar will send a beep sound, and she will stop and turn back. When just started the training. If the dog keeps going forward, a mild shock may be sent from another button.
For the stimulation I use levels 2 and 3 the most often. When the dog hair is long or the battery level is low, I have to either use a tighter fit for the collar or increase the shock level. I often try on my fingers before put it on my dog. Level 4 is really uncomfortable. The shock will make the finger muscles shrink, and feel sour and numb. I rarely go above level 4.
Both the transmitter and E-collar are rechargeable and they can be charged at the same time. It is claimed to last 50 to 70 hours for a two-hour charge. As I only use for a short time each day, it may last for about two months after a full charge. When the battery is low, the yellow-green indicator light on the E-collar will turn red.