You hire the boat, not a seat on it — the price is the same whether two of you come or the whole group. A skipper comes with it, so no licence is needed and nobody has to spend the day navigating.
What you can hire
Malu V · by the hour
A Tullio Abbate for a half-day along the coast or a full day out. You choose the departure time and how long you stay. From 150 € for one hour, up to 1.000 € for eight.
LYA yacht · by the hour
The quieter option, with room to sit and shade to sit in. 200 € per hour for the boat.
How it works
Pick the day, then the length of the trip, then the departure time — in that order, because which times are free depends on how long you want the boat. What you cannot have is greyed out rather than hidden, so you can see why.