Couple of ideas (our masters team is pretty well attended, on average I'd say around 50% of our members are at any given practice.)
We run practices Monday - Thursday evenings, Sat AM, and Sun AM, Sun evening.
Sunday AM is our LC practice.
Sunday evening is our lightest in terms of attendance.
1) evening practices start at 7pm or 7:30. Gives people enough time to get home from work, have a bite to eat, and still get home from practice at a reasonable hour
2) each practice has at least 3 lanes (slow / med / fast, although that's not what we call those groups).
3) social events. We do a monthly brunch after saturday morning practice, and monthly "pool to pub" night, usually the last thursday of the month. That helps to form friendships, and people are more likely to come if their friends are there.
4) the board meets about once a month to discuss issues that arise, any concerns that the members have, and we try to address those ASAP. That includes addressing things like etiquette in practices.
We have 2 coaches (paid) at any given time, they alternate nights. Coach A runs M / W / Sun PM and coach B runs T / Th / Sa / Sun AM. Coach B is the now retired former head coach for the local University varsity squad and largest AG club in the region. Coach A is young (couple of years post graduation) a former swimmer at the same university. Having 2 coaches, with different styles, lets people pick and choose which practices they like best.
Rates - we probably undercharge.
We also have an arrangement with the pool that our members can drop-in to any public lane swim at no extra charge. There are a number of swimmers who take advantage of that all the time, they do more lane swims than coached practices.
Swimming Workout of the Day: Favourite Swim Sets: 2020 National Masters Champion - M50-54 - 50m Butterfly