Here's a quick primer on the beaches/lagoons around the island, including some dining and accommodation options. Keep in mind that the island is rather oval-shaped (nearly circular yet wider east-to-west than it is north-to-south), The island is approximately 5km across, with a basaltic central interior that is mountainous and without roads. Rarotonga is a reef protected island, meaning that rougher waves of the ocean shatter the offshore reef resulting in calmer water near the shoreline.  Stretches of lagoon offer conditions near perfect at times for snorkeling, swimming and kayaking..Most areas of the lagoon are not suitable for surfing; except in a few patches along the northern side of the island. Surfing is best carried out by experienced surfers, and in the company of locals who know the tides and prevailing conditions.

Starting in the NW corner of the island and working clock-wise around to the starting point, the total distance along the main road is approximately 31 kms (about 20-25 miles or so).  A drive around the island will take 1 hour given the speed limits of 50kph, and even 30 kph in certain areas. 

North side of Rarotonga  - Near the airport (located in the NW area) there is a fairly wide lagoon providing good snorkeling, swimming and reef fishing. As you move eastward, the lagoon narrows dramatically, until the reef is essentially up against the shoreline, resulting in rougher waters, unswimmable in parts due to corl heads with somewhat of a dramatic appearance. This remains the case pretty much along the entire north shore. The main town area & ports of Avatiu and Avarua, retains a number of shopping and dining options (including the Tamarind House restaurant, owned and operated by Sue Caruthers - one of the more well-known restaurateurs). With regards to accommodation, there are few  rental bungalows, in addition to the multi-unit Paradise Inn (catering to travellers on a modest budget), Club Raro (which looked pretty nice outside from the street, but has a limited swimming lagoon area) and the older-style Kii Kii Motel.

East Side - The NE lagoon is similar to the north with the reefline being closer ashore. The northern end of Muri lagoon is extremely scenic  with reasonably calm and clear water.  Aroko on the Muri lagoon has a saltwater marsh, a tranquil lagoon traditionally used for fishing, and several lovely offshore motu (islets). Accomodation in this locality including Sokala Villas offer spectacular views across the lagoon to the motu. The water here is very shallow (waist deep or less at low tide) with a smooth sandy bottom but few fish (since there is no coral for them to hide in). The current towards the lagoon outflow at Avana harbour (between the mainland the northernmost motu in the vacinity of Avana Marina Apartments is VERY strong and dangerous if you get near the outflow. Away from the harbour, the lagoon is generally very safe and shallow.  It is relatively easy to wade over to the uninhabited offshore motu to explore and spend an afternoon pretending to be Robinson Crusoe.

In front of the Pacific Resort, the lagoon widens towards the reef and becomes deeper (deepest part of Raro's lagoon). The scenery here is beautiful, and is the most photopgraphed of all locations on Rarotonga. Muri is the heart of Raro's tourism area and it is fairly "congested" (a relative term on Raro, considering that to most folks no part of the island is "crowded"). There are several good places to stay here, at a variety of price points.  Accommodation includes the Pacific Resort, Muri Beachcomber, Muri Beach Resort and  Vara's. There are also a number of good restaurants such as Sails, the Flame Tree, Pacific Resort and Aqua. Sails and the Barefoot cafe at Pacific Resort offer great views from their outside dining areas. This is also the area for water based activities like sailboarding and the start of the lagoon cruise.  If you can time your trip so that you coincide with the full moon, these are great places to watch the moonrise over the eastern horizon.  Strolling along the shoreline in a northerly direction provides the best opportunity to observe a full moon illuminating the lagoon and the offshore motu. Pure magic!

The southern end of Muri with the southernmost motu, especially around Te Manava and  Rumours can be a bit rocky in the shallows, with wide, flat (but rough) sheets of coral stone, making wading a bit difficult sometimes, but resulting in some nice tidepools near Rumours. Further on as you head south and west, the bottom changes from sheets of coral to coral towers separated by sandy areas - perfect for wading, swimming and snorkeling. Since the prevailing tradewinds blow towards Tikioki, this area is generally considered to have the best snorkeling on the island, but it is almost more breezy as well.  One of Rarotonga's established marine reserves is located in the Tikioki lagoon. Reflections is situated on a part of the beachfront that depicts the start of the deeper water well suited to swimming and snorkelling. A number of small, private rental bungalows occupy this stretch of the beachfront also. During the hotter months (Dec-Mar) the tradewind breeze is especially welcome.  But the cold winds that arise along this side of the island can become chilly during the cooler months (June-Sept). During times of Dengue outbreak (which can occassionally occur in the Cook Islands), this area tends to have the least vector problems, since mozzies are such poor flyers in windy conditions.

South Side - This district offers wonderful snorkeling with the lagoon profile being a mix of smooth sandy floor scattered coral heads and dazzling aquamarine water. It's in this eastern part of the southern shoreline that the Fruits of Rarotonga cafe lies, This is often mentioned as the best single spot for snorkeling on the island. It attracts quite a few visitors on a daily basis. If you purchase a smoothie (which are quite good) at the Fruits of Rarotonga, they will apparenty watch your gear while you swim. Also in this region are the well-regarded Rarotonga Beach Bungalows and hotels including Moana Sands and the Little Polynesian. ALL of this Tikioki - Titikaveka area has great snorkeling. There's limited choice with regards to dining -both the Moana Sands and Little Polynesian restaurants have good reputations. 

The rest of the south shore, all the way out to the Rarotongan Resort, provide near uninterrupted and enjoyable snorkeling conditions; again the lagoon has a smooth sandy bottom and scattered coral towers. The lagoon around Titikaveka is wide (near 0.4 kms) and the waters calm and clear. This is an area dominated mostly by private homes and small rental bungalows, with only 2 resorts Sea Change (upscale property) and  Palm Grove. The area around Palm Grove has nice wadeable water (waist/chest deep) out to about halfway to the reef with deeper water beyond that. This area tends to have pretty much empty beaches (not that the beaches anywhere on Raro tend to be all that crowded).  Generally traffic here is the lightest on the island, but as more and more development occurs, traffic around Rarotonga anyway is increasing. There are only a couple of places to eat here (Yellow Hibiscus at Palm Grove, Vaima restaurant, a coffee shop at Moana Villas and Wigmore's Takeaways). Wigmores super store is immensely popular at all times of the day.

West Side - Beyond the Rarotongan beach Resort and further towards the extreme SW corner of the island marks the transition from the wide  lagoon area to the more narrow (mayby 100 meters to the reef) and shallower (waist-deep or so) western side. The snorkeling near the Rarotongan is extremely good since it is also area a marine reserve protected from fishing.  The western side of Rarotonga is the second most popular area for tourists to stay, undoubtedly drawn by spectacular sunsets among other scenic attractions.  There are lots of accomodation options and a fair number of choices with regards to dining. Arorangi is home to Raro's largest resort ( Edgewater Resort)  There are some very nice accommodation places along here including Crowne Beach, Manuia Beach and Sunset Resort, and Sunhaven as well as smaller collections of rental bungalows. This area is generally more sheltered from the wind so it tends to feel a bit warmer than either the east or south shores and have a bit more of a mozzie problem. It's also sunnier and drier yet lush and green. As you approach the northwest corner of the island the snorkeling improvesat Black Rock, as well as along the extreme northwest corner (western end of the runway).  A further marine protected area lies in this vacinity where fishing is prohibited.

This completes the entire circle around the island. All of Rarotonga is beautiful.  Each district of the island offers distinctly different beaches and lagoon profiles.  

Pollution concerns within parts of Rarotonga lagoon are being resolved. Visitors are probably best advised to avoid swimming near streams during heavy rains when runoff into the lagoon will affect the water quality for several days.