Diani Beach is generally safe for swimming, with a protective coral reef about 500 meters offshore that breaks waves and creates a calm, shallow lagoon ideal for families. Water depth varies with tides—high tide offers deeper swimming, while low tide exposes coral and restricts access. Beach resorts often have lifeguards, and water quality is monitored. Be cautious of sea urchins in rocky areas and respect posted warnings about currents near reef gaps. Petty theft can occur on the beach, so keep valuables secure and use hotel safes. Overall, Diani is one of Kenya's safest and most family-friendly beaches.

Diani Beach enjoys excellent weather year-round, with warm temperatures and swimmable seas in every season. The driest and most popular months are January to March and July to October, offering sunshine and ideal conditions for water sports, snorkeling, and sunbathing. December and late June are also pleasant but busier with holiday crowds. The rainy seasons (April–May and November) bring afternoon showers but fewer tourists, lower rates, and lush greenery. Even during rains, mornings are often clear, so budget travelers can still enjoy the beach with occasional interruptions.