I'm assuming that you took the Red Cross ceritification training for the pool. Unfortunately, over 95% of privately owned and operated waterparks across the entire world certify their lifeguards through Jeff Ellis & Associates. (it's more commonly abbreviated to just "Ellis")
Ellis has an International Lifeguard Training Program (ILTP) that you may be able to take on your own if it's offered somewhere or you may have to apply for a lifeguarding job at a waterpark first in order to be able to take the training course. I applied for a job as a lifeguard at a waterpark and that's how I came to know Ellis.
Completion of the course will result in your certification from Ellis but certain waterparks may choose to restrict your attraction training due to things like age if there are particular circumstances (such as moving belts that carry large tubes up to tower tops).
In order to continue with the course you have to pass a series of prerequisites (which really aren't that hard). You have to swim a total of 200 yards on your stomach with your face never going underwater (so less-intense breaststroke or a sloppy freestyle work well), retreive a 10 pound brick from the bottom of a 10 foot pool (sometimes it'll be a 12 foot pool or the deepest spot in the waterpark) and you have to tread water keeping your arms above water for 2 minutes. If you fail to meet any of these prereqs by the time the class is completed you'll have to forfeit any money that you paid to take the course and you'll have to pay for another course and take the whole thing over again.
During the class you will be required to go over CPR and AED use (every single day in most cases) and you'll also have to learn things like airway obstruction treatment (there's a lot to cover there), symptoms of heat stroke and hypothermia and what to do, symptoms of heart attacks and strokes and how to treat them, head/neck/spinal injury treatment (both in the water and out of the water), rapid extrication of a "guest in distress" (or otherwise known as "Gid") from the water ("victim" is considered a taboo word in the ILTP) and the various kinds of water rescues that you may have to implement.
Once you do all that then you have to take a written test and get at least 80% of the questions correct (it's really not hard if you know what you're doing, I got a 98 my first year and a 100 this past summer). After that it depends on the waterpark that you work at.
All of this might sound like a lot of work but it's honestly really rewarding. The pay may not be that great but you can still know that you worked really hard and there's a lot of chances for promotion from within if you want to explore those options. I actually applied to be a Head Guard for this coming summer (they're a regular lifeguard's immediate supervisor) and I can say from experience you have to have a very mature mindset and not take the job as any old job if you really want to do well. Letters of recommendation from a waterpark go a long way since almost all waterpark managers will mention that you had to work really hard to get the job (and also to keep the job since random mannequins can be placed in your water at any time and Head Guards and other supervisors can determine how well you're scanning your water). It's also a great way to meet a ton of people and typically all amusement park personnel get special benefits like free admission to the park and discounted admission for up to three other people on your days off in addition to food discounts and special operating times reserved strictly for employees.