ACCESS TO WATER
There are no Waterfront style lots in this world.
The Lake that Lakeview Apartments are named for? Literally, just a view. Can't even wade in it. It does have an "island" though (it's connected by a walkable spit to the mainland). An island with a mirror....
There are also several real islands in the ocean near each mainland, some of which may have treasures to find. A couple of them could also be good places to play at be Castaway, as long as you keep your camera facing away from the mainland. There are no lots on the islands, but there's enough open sand for a night or two's stay.
Swimmable Areas
There is access to the ocean (via the open street) from every lot in Ondarion but you might want a bike, broom or teleportation method if you live on the inland side of each region as it could be a bit of a hike.
The biggest beach in each 'hood is your best bet, as some of the smaller beaches are only accessible from the ocean side.
The swimmable/sailable areas are clearly delineated with a series of buoys, so you can see how far out you can go at a glance.
Fishing Spots
Verdemar - Verdemar seems to be the most fishing-friendly town, which makes sense as a home of pirates and adventurers. Both Starter lots are right next to fishing signs. One is an ocean fishing spot on small beach by the Fisherman's Hut starter home, and the other is a river fishing dock by the empty lot in the north of the region (The Lair in the Open-Air). There's a third sign by the lighthouse (left side of the marina on the map).
Dambele - There are two fishing signs in the same general area in Dambele. One each side of the main beach, on the docks. The region is a desert, so the inland water is Sim-made fountains and reflecting pools, rather than natural bodies of water with fish.
Bellacorde - The least fishing-friendly with only a single fishing spot on the pontoon at the marina, this region is more likely to sail on the ocean, than drag denizens from it. Far more high-brow.
New Boats
Sims can also sail and fish from the new boats. These look like small sailboats and come in a variety of hull (wood) and sail colours. They cost 2500 each, and are basically the same as the [IL] Island Canoes, but for rich/fancy Sims. They can also be placed on your lot as décor and wouldn't look out of place in other coastal towns like Brindleton Bay.