Gains: stability
Two hulls barely roll. If anyone in the group gets seasick, this is the answer.
Two hulls
Flat, shallow-drafted and enormous on deck. The right answer for a group where most people are not diving.
A catamaran trades the cabin count of a phinisi for stability, shallow draft and deck area - it barely rolls at anchor, it can sit closer inshore, and it suits groups with more snorkellers than divers.
The trade
Two hulls barely roll. If anyone in the group gets seasick, this is the answer.
Sits shallow, so it anchors closer to the reef and inside bays a deep hull cannot enter.
Trampolines forward and a wide aft deck. More usable outdoor space per metre than anything else.
Fewer and smaller than a phinisi of the same length, and a tighter dive deck.
Groups where the diving is part of the trip rather than the whole point. Snorkellers, children and anyone who would rather be on deck than under it.
Anyone worried about motion. A catamaran at anchor in the Gilis is about as still as a boat gets in Indonesia.
Not the choice for a hard dive week. A phinisi or a purpose-rigged dive boat has the deck and the tank capacity for three dives a day across a group.
Send dates and group size. If a catamaran suits and one is available we will say so - and if it does not, we will say that too.