Oh deary me. Gosh. Where do I start?
Since it's gone from generalities to personal, I'll chip in with some personal anecdotes as well then.
I know from personal experience that not all sea sports are "cooling during hot weather". Especially sailing and kayaking where you aren't supposed to be actually in the drink. If you splash seawater on yourself to cool off, when it dries, the salt crystals on your skin make the sun's effect worse. Sailing and Kayaking and any sea sport where you stay dry(ish) is hell in bright, sunny conditions. Give me overcast anytime (except while diving) - more wind, more cooling.
Also, I conflated nothing. I simply tried to give examples of some common sea sports and how the local conditions aren't conducive

I mentioned surfing because we have absolutely no waves to surf on. I didn't mention windsurfing now did I?
That said, surfing is actually possible in Singapore, I've done it myself. You can do it at the Wave House. Even snow skiing is possible in Singapore (@Snow City). For the uninitiated, those 2 venues are artificial wave and snow slopes facilities in Singapore.
Facetious as my clarification may be, it is a deliberate counterpoint to your assertions that you can windsurf/foil, wing surf/foil in Singapore. Yes, you most certainly can, despite our "tame winds". Just like you most certainly can surf and snow ski in Singapore in our ersatz facilities. But the reality is that these conditions are very borderline and very much suitable only for conducting the most basic of activities and beginner lessons. Yes I actually do participate in a lot of sea sports and I can tell you that you will very quickly tire of the "tame" ,beginner friendly conditions here.
Also, you can kite surf in Singapore without a board. My friend (no, not Chow Yuen Fatt) who kitesurfs regularly will disagree with you that you need a boat to do it in Singapore.
I don't know why Chow Yuen Fatt is even being mentioned at all. I don't quite see how Mark gor's involvement legitimises aquatic sports in Singapore but I will be sure to ask him next time I say hello to him across the driveway. Maybe he can endorse my sport(s).
And ... Scuba is not a sport? My, my, my. The next time I am in Zhanjiang for a meeting with the president of CUA/AUF, I will be sure to inform him that CMAS has it wrong. Scuba is a sport under the auspice of CMAS, along with quite a few other sub-aquatic sports which you probably have never even heard of. Ever tried underwater rock rugby? I have, when I was diving in Japan. It happened in salt water, off the beach, so it is a sea sport?
Scuba may not be ideal in Singapore but I can assure you it is not just because of urban runoff. Land reclamation wreaks havoc with underwater viz too. But maritime traffic definitely plays havoc with Uw viz in shallow channels. I've done a few hundred dives off the Malaysian islands where cruise ships sometimes go by to know the difference. Multiply that by the frequency of large ships going around Singapore and you tell me it's not a factor. My forum nick is also my bottom gas of choice. When you figure out what that is and what type of diving it entails, please come back and tell me again that what I do isn't a sport or I am not adventurous or even that Scuba is not a sport.
Singaporeans are definitely a different breed from HK'ers. The HK'ers I met in Uni are by and large urban cowboys with some rare exception. By contrast, every Singaporean son is a soldier as well and are easily more outdoorsy and more willing to get sweaty/dirty than your average HK'er.
Also, Yes, in the sea sports scene the gwailos may be over-represented compared to their actual percentage of population but our seasport scene is definitely majority locals. That the HK's scene is majority gwailo does prove the point that Singaporeans are more sporty.
There is high separation between maritime traffic and our sea sports activity zone? Tell that to the bulk carrier bearing down on my laser giving us warning toots on her horn. That happened when I was sailing off Seletar. Tell me about the separation again when I am on a southern coast traverse on my ocean kayak, especially when I am rounding Sentosa with the currents and port.
Sailing, as with many water sports from Singapore, their competition success mostly stops at the Asiad level. We are capable of dominating the regional scene but once we go on the global stage, we are very much found wanting. What sailing is though, is it is very well funded as it is one of 2 sports identified by the government as high potential for olympic success given our physical disadvantages in many other sports. Most other sports federation don't look very kindly at sailing/shooting as these two sucked up al l the sports dollars and our federations were plundered to fund them - and they still haven't produced Olympic gold which is the KPI. HK has though in sailing. Don't sell your own hometown short.
No you are most assuredly not quite mad dog status yet. If you haven't played the classic Englishmen sport of rugby or cricket in the mid day heat, then you are most assuredly not a mad dog yet. When you have, come talk to me again about how you managed to infer so much about me from so little info and what really defines sporty or adventurous...
Meantime, this is very much ot from coronavirus so I'll stop here.