Until about 10 years ago Speedo type suits were made with non-stretch Nylon fabric. First thing I did with all of mine was to cut out the liners. It made them more comfortable and slightly see-thru when wet, which was what I wanted. They still gave good support.
Now they are made with stretch fabric but the liner has little vertical stretch, to keep the gear under control. I cut out the liner and found that the suit went all out of shape in the crotch and also was not see-thru like the old ones. I don't like the new ones at all but cannot find the older non-stretch type.