On slow days you have to look at waterpark labor as a fixed cost like a mortgage payment or insurance fee rather than a variable controllable expense.Meaning it is comparable to the fact that the bank expecting the same mortgage payment amount regardless of you low income that month. the mortgage payment never goes down as a percentage of your revenue.
Of course you can always trim labor but as anticipated revenue goes down lifeguard labor can can only come down proportionally for a very short time until you are spending more in the short term than you are making.
e.g. the cost of minimum staffing maybe 1 guard per ride/pool open with someone to rotate for breaks which may far outweigh the revenue coming in from one or two families that may visit.
You may not now when and for how long those small amount of guests may come so you have to have the staffing staggered appropriately. those guests don't really care that you may be losing money but you should care that you provide an experience that your guests are paying for.
Just a change in mindset as you'll never see Waterpark labor in the fixed expenses of the P&L. There is nothing wrong in asking for ways to reduce labor costs but all non lifeguard executive management need to understand this and lifeguard managers need to remember this.
Keep in mind, on those busy days your labor % may be well under the expected goal and you wont be allowed to bring in more lifeguards so you have one for every guest in the pools and on the rides.