The most popular water activities in Sanremo are boat trips (sightseeing tours, dolphin photo-hunts and tours of the French Riviera). Scuba diving or snorkelling is another common service on the coast; thanks to the absence of waves in Sanremo there is a good overview of the seabed.
If you want to go scuba diving in Sanremo, try the family-run Polo Sub in Via Lungamare 1 - they have tried and tested equipment, friendly staff and free parking spaces. Scuba diving clubs in Sanremo such as Centro Immersioni Aton and San Remo Sub are also popular.