Here is a two-day Alibaug plan that accounts for the things people forget: heat, ferry schedules, and needing to eat.
Saturday
Morning. Early ferry from the Gateway. You will be at Mandwa by mid-morning, hungry.
Eat first. Breakfast is two minutes from the jetty and runs to noon.
Midday. Check in, drop bags, head to the water while it is calm.
Early afternoon. Get out of the sun. This is not optional in most months.
Late afternoon. Sundowners. Be seated before the light starts to go.
Evening. Saturday means live music. Stay for it.
Sunday
Morning. Slower start. A long breakfast is the correct move.
Midday. One thing, not four. Kolaba Fort if the tide suits, or a quieter beach like Kihim.
Afternoon. Lunch, unhurried. Then head for the ferry.
The two rules
Do not over-schedule. Alibaug punishes packed itineraries. Two things a day is plenty.
Check the last ferry before you plan dinner. Every time.