The only trait I can think is Love the Outdoors which they both have as well as Athletic as they don't have any of the water traits either

Maybe it is trait related according to the sims 3 wiki both the Love the Outdoors and Athletic sims are attracted to beaches and pool and since they have both it kinda makes sense

I uninstalled Island Paradise since I was getting fed up with random boats that suddenly appeared in inactives' inventories. Just watch out when playing in a world such Riverview, Roaring Heights or Moonlight Falls where residents can go across the water.

Not sure you can stop the interaction with the water. Sims are going to use the shortest route. If that happens to be in water they are going in the water. The core doesn't care about Retuner in that case. I'm sure there's something I could force in the routing code but that's another discussion.

Sorry to mislead anyone. I should have clarified my suggested settings were in ocean water not lakes or rivers. Retuner and GoHere took care of autonomous Swim Here and Boating issues in my worlds. I only have one world with a large lake but have not noticed sims swimming to get to a particular destination. Perhaps because I've got subways all over the place. I often see animals swimming across but after a bit I've seen them using the subways rather than swimming across, lol.

Well here's what I did I placed a 7 subways 1 in the middle of the island and and a subway on the opposite sides of all the bridges and used S3pe to find the SimRoutingComponent_0x7728186024b1edce XML and changed the kNPCSubwayUseChance value to 1 and then changed kDistanceMustSaveInOrderToUseSubway value to 1500 so far their using the subways and not trying too swim.

@sittingbear - That's great but at +1500 for that second value, do you not find that sims are forced into subways even when it doesn't make sense for them to be in one (unrelated to water) or is Riverview's map large enough to withstand a value that high?

Now all I need is to find away to get them to stop tapping their foot and stomping their feet on a route failure, after all these years it's just now starting to annoy lol

That probably is a little to high I'll have to play around it the subways except for the one on the island are really close too both sides of each bridge

Well as close as I could get them anyway