This post will highlight which Superior Water Villas (SWVs) have the best views. Villas are listed in numerical order (from northernmost to southernmost). Please feel free to let me know if you have any pics that you think would be worth adding in addition to the ones below.
Background
There are 12 SWVs, 3 blocks of 4 villas each. Villa numbers are as follows;
Northernmost block: 331 - 334
Middle block: 335 - 338
Southernmost block: 339 - 342
Links to maps showing villa location & numbers:
New Map (Resort's website) (2017, PDF) and
Old Map (Resort's website) (2014, PDF)
Corner Units: 331, 334, 335, 338, 339 & 342
Orientation
Note that the 12 villas are not facing due west; 331-338 face WSW and 339-342 face almost a SW direction, and so the sun is a little to the right if you are in the villa and looking directly out towards the ocean.
Views
Some SWVs have their views obstructed by the Over Water Spa (OWS) and are less desirable as far as having unobstructed views of the ocean is concerned.
331
The view from this villa is unfortunately largely obstructed by the OWS(Over Water Spa). See following pictures (courtesy AICML and MS02113) of the view from this villa
332
If you are seated near the sliding deck doors, you won't really see the OWS. However if you are on the sun loungers or in the whirlpool you will be able to see it. Pics (courtesy slappychasez) follow
333
The view looks uninterrupted. Pic courtesy of Wozza2404
334
Pretty sure views from this villa are totally unobstructed however pics would confirm this
335 - 342
Since these 2 blocks of villas are situated further south and are at a better angle (facing more to the west) than the first group of 4 (331 - 334), they all have good views of course but if I had a choice out of 334 and 335 I'd choose 335 as you would probably see 335 out to the far left if you were sitting on the far right hand side of 334's jacuzzi. (If you were in 335 you wouldn't be able to see anything to the left or right, not even 334.) This is because the northernmost block (331 - 334) is not facing west at the same angle as the middle block; it's facing slightly towards the middle block (335 - 338) (check positions on the maps linked above to see what I mean) and as a result you can see 335 from the left hand side of 334. The dividers / privacy walls are on the right hand side of all SWVs so the left hand sides are somewhat open and you can see the outside (privacy wall) of 335 to your left should you be near or at the edge of the deck of 334. Except for this one situation, you can't see any other villa should you be sitting right at the edge of the deck of any other SWV because they are set back from each other as they go south. As an example; in 339 I had maybe a 150 or 160 degree panoramic view when sitting on the edge of the deck facing the ocean, so even when sitting at the edge you couldn't see any other SWVs. Great stuff because all you see is endless ocean as far to the left and right as you can see. (The reason it wasn't 180 degrees is because of the privacy wall on the right hand side.)
Snorkelling Views
As previously mentioned I have stayed in 339. I have also stayed in 338 and if it came down to a decision between 338 and 339, I'd take 339 as if you wanted to be a little adventurous in your snorkelling I'd have to say it's the best one as it's easy to skirt the coral formations outside the villa and go around the back of them and cover more ground, i.e; you'd go almost directly west from the villa and circle round the darkest, most dense patch of coral making for a slightly easier and slightly better snorkelling experience (check Google Maps for locations of coral formations - they are the dark patches you see in the lagoon). Also, if you want to be really adventurous, I have walked / snorkelled right out to the edge of the lagoon and back and it required much less effort from 339. Tip: If anyone does decide to venture far away from their villa, put some brightly-coloured cushions or something similar on the edge of your deck. This will make it much easier to navigate back as it's a good 400m out to the edge of the lagoon and it's useful to have a reference point so you don't wander too far north or south.
If you have small kids and didn't want to venture too far away from the villa then 338 would be your best bet as you'd have coral and lots of fish on both sides after you got down into the water from the stairway on the deck. Be sure to snorkel at low tide as kids can easily walk around on the bottom and they're not constantly having to stay horizontal and paddle.
Note that you can swim over most of the coral formations on the western side of Rangali Island with a reasonable degree of safety but only at high tide. Anything lower than the near highest or highest water level and it's a little too dangerous because when you kick your feet to paddle you could quite easily hit the coral. That and you'd need to wear a life vest if you weren't that good at keeping bouyant. Touching / damaging the coral is a big no no as you are most probably aware.