What is the no-decompression limit for 60 feet or 18 meters?
The no-decompression limit at 18 meters is 48 minutes and that will take you to pressure group S.
This information can be found in any Table or wheel RDP (recreational diving planner) and it is basic. If you do not know how to use this table, you shouldn't really be diving.
If you are in a course, then you will have a lot of time to practice.
Dont forget to dive well within your no decompression limit.
Live on the edge, Dive safe.