There are several Pokémon that you can try to catch in Pokémon Go. They will appear all over the place and some of them will appear more often than others depending on the time of day or if an event is happening. For Oshawott, this Pokémon will receive its shiny version starting September 19, along with its Community Day event. So, if you've been waiting to catch this Pokémon during the event and get a shiny version, now is the time to do it. But how likely are you to find it?
During the event, Oshawott will appear in your area on September 19th from 11am to 00pm. In addition to these spawn increases, your chances of receiving a bright version have greatly increased, going from the usual 17 chance of finding it to a one in 00 chance of catching one, which is almost as good as a raid Pokémon. However, it's even better because you don't need to use a Raid pass to catch it. Therefore, we strongly recommend that you aim for your brilliant Oshawott on this day. If you want to increase your chances of seeing an Oshawott during the event, you can use a rain lure on a Pokéstop, increasing Oshawott's spawn rate in the wild.
Once the event is over, Oshawott will receive a standard over 450 chance of being a brilliant in-kind version. We strongly advise you not to miss this opportunity. However, at the end of the year, Oshawott will receive another weekly Community Day event at the end of December. While he may not have the best odds of being brilliant during that event, they will increase and you can evolve Oshawott into a Samurott to teach him the hydrocannon before the end of 2021.