Scoring

Para Swimming has a functional classification system offering 14 different sport class: 9 for those athletes competing with a physical impairment, 3 for those with a visual impairment, and 1 for those with an intellectual impairment. None of these are diagnosis dependant but are defined by degrees of "activity limitation for sport".

This combination of 14 sport classes and two genders means that it is rare for a swimmer to race head-to-head against others in exactly the same sport class and juding who wins a race requires metrics other than time. One common means to rank performances is with a points chart or calculator.

Designing these is a nontrivial problem. There are several system in common use all of which choose a different set of tradeoffs.

Example Scoring Systems

World Aquatics

As a baseline World Aquatics (formerly FINA) describes their scoring system here.
This system, with some refinements, has been used for a very long time originatating with Nick Thierry.
At the heart of this grading curve is an inverse-cube.

World Para Swimming

For the purpose of ranking performances over the course of the World Series WPS points are:
Described here. At the heart of this grading curve is a gompertz growth function.
A calculator is available here.
Tradeoffs include: only observes international results and, as such, cannot score developmental results (scores reach 0pts quickly) and data for events not on the Championship Programme deterioiriate quickly.

Swimming Canada

Used to determine place finish for all levels of competition, this system uses a modified version of the World Aquatics calculator relying on a rolling 4 year average of highly ranked swims (not world records) and a curve that varies (based on depth of field) between an inverse-square (less DoF) and an inverse-cube (more DoF).
Depth of Field and sample variance are used as a proxy for varying performance development. Anecdotally it's noticed that greater levels of activity limitation tend to trend with both shallower depth of field as well much more "hockey stick" shaped individual performance development .
Swimming Canada offers a calculator here.
Tradeoffs include: difficulty scoring exceptional world class results, events can still be distored by outliers, no attempt is made to score events outside of those eligilible for Major Championship programmes.

British Swimming

Similar to the World Aquatics system we see here an inverse cube and (largely) world record anchor points
A calculator is available here

German Disabled Sports Association

Something between the Canadian and British systems in design achor points per event are set (roughly) using world records. More on that in a moment.
Curves do vary between sportclasses but discretely, not ona spectrum. Those sport classes with the greatest activity limitations use an inverse-square, those with the least and inverse-cube, those in the middle use -1/2.5.
In the Olympic programme each stroke is contested over differing distances based on the event ex: both the 100m and 200m butterfly are medal events at the Olympics. In the Paralympic programme each stroke (saving freestyle) is contested over one distance per sport class ex: S7 50m butterfly and the S8 100m butterfly.
The German points set their anchor points using the best ratio of the WPS world record in the sport class for the stroke vs the World Aquatics World Record for the stroke in that gender.
More information is available here
Tradeoffs include: some effort is made to account for depth-of-field (like the Canadian system) but underscoring for some sport classes remains an issue.