There are a few lagoon cruises on Aitutaki. We were extreemly happy we chose to go with Kia Orana! They pick you up on time, take you to some beautiful snorkelling spots (when no one else is there so it's completely private!) and take you to a quiet island that is completely private in beautiful Aitutaki lagoon. You get to spend a few hours there enjoying the pristine beaches, water, and delicious meal of fish, and fresh fruits.
A must if you are in Aitutaki!