This is not at all unusual for any server on the public Internet. There are a few steps you can take to reduce the risk from this. You have indicated you already set up fail2ban which is a great step.
You can change your ssh port. Since most of these brute force attacks are automated and usually target the default port 22 this would further reduce the number of attacks on your ssh service.
You could set up CloudFlare's free reverse-proxy plan in front of your droplet. Since ssh is not proxied a user looking up your domain name would only receive a CloudFlare IP. This will not prevent indiscriminate scans but would help a lot with any attack that may be targeted at your domain.
You can report these instances to the network operator of the IPs you are detecting. Operators in many countries will take action against this activity, unfortunately in others these reports may be ignored. You can usually find the abuse email address by performing a whois on the ip address: