It opens up possibilities like open sea swimming, surfing, canoeing - and as an island there's lots of opportunities to have these experiences.
The reality of this is none of these activities are really open to kids or adults who come from deprived communities anyway, even if they can swim.
Why?
Because the equipment isn't cheap. And if you want to do it safely to any level you need to pay for lessons which are even more expensive. And they are very much location based.
DH got qualified in kayaking to give kids the opportunity - especially kids who are from more deprived backgrounds - through scouting. But even then, the reality is that is extremely difficult to do that outside scouting if you are from that background. They do run sessions very cheaply, but those kids still have to GET to that base. It DOES widen who gets the opportunity to do those things but the reality is that it still doesn't give it to all.
He also would argue that ability to swim doesn't prevent you from canoeing or most kayaking in practice because of modern buoyance aids - confidence in water is more important for entry level (and minimums of being able to swim 25m are more about ensuring people won't panic on contact with water rather than being inability to swim is prohibitive). Its preferable you can swim well but not necessarily essential. Most companies will say it to cover their arses with insurance / safety rather than because of the need for skill.
The thing that scares him more is people who can swim thinking they can kayak/canoe and buying cheap inflatables going on whitewater or on the sea (especially with no buoyancy aid) and then getting into trouble. If you can't swim, you won't buy a boat of any kind and go use it irresponsibly. He saw one in Asda the other week and swore - its irresponsible for them to sell (I believe a number of Decathlon stores stopped selling them for a while because of problems).
It then falls on the paddling community to do life saving exercises. He has numerous friends and acquaintences who have ended up doing this, because of feckless idiots who think they can just take out a boat precisely cos they can swim but have no idea of water safety. This endangers their lives in the process (their qualifications to teach stipulate that they have responsibility to intervene if they see random people doing stupid shit or getting into trouble - they are potentially liable if they just walk away).
Indeed the number of recent incidents involving paddle boarders without buoyancy aids is so bad that it looks likely that they will be taken under the guidance of the BCU (British Canoe Union) to improve the standards on water safety and advice out there because the sport has been so poorly governed. Over confident swimmers are as deadly as non-swimmers without the water safety knowledge.
That is why, I do think water safety / confidence should be higher on the agenda, rather than swimming itself.
I don't think being able to swim opens up a huge amount more opportunity in reality (I say this as someone who can just about do 25m in a pool but wouldn't in the sea). It could improve health issues for some as an alternative exercise, but not really opportunities as such.