Underwater
There are outstanding locations for snorkeling or diving. Some are even close to the shore and not a boat necessary. Share special places you know and describe what to expect.
May to October, with a great start in May when a mass of cuttle fish enter the estuary to spawn
Netherlands 
Valle Verzasca is a beautiful valley and impressive throughout the year. If you like to come here for swimming, diving or snorkeling the season starts in May until October. The mountain river is pretty cold and a wetsuit is necessary to stay in the river for a while. The water temp is more bearable in August/ September. Best light from 10 a.m. until 2 p.m. If you arrive afterward the rock garden is less impressive without any sunshine into the river.
Crowds
Peak season and utterly crowded in July and August. Our preferred month is September, fewer crowds and less cold. Avoid the crowds at weekends.
Check the weather forecast first; sometimes flood waves can happen. Weather Forecast
Switzerland 
Snorkeling during high tide only! Please avoid low tide to protect the corals. At low tide the water level is too shallow and you may destroy corals while you are snorkeling. Check the tide times either at Milyering Visitor Centre or follow the link. Tide Times Exmouth
Weather
The region has a tropical-hot-desert climate. In autumn and winter from April to September with pleasant temperatures around 25° C which cause an average water temp of about 22°C. It's hot during summer with an average daily temp of 35°C and water temperature around 26°C. It doesn't rain much here; less than 30 days of precipitation with the highest chance for thunderstorms from January to April. Fewer clouds from August to December. Cyclones can occur and are more likely to happen from January to March. In March 2015 Exmouth was hit by one and at the end of April 2014, record-breaking heavy rainfall caused flash floods.
Australia