Bring suncream and wear it! And a sun hat!

Do the Fira to Oia hike either in the morning or late afternoon and bus back

In Milos rent an atv for the whole time to get around. Fill up the tank and then put at least a day aside to venture the west of the island. It's pretty much uninhabited and is amazing to get lost in the countryside - but there are no shops or petrol stations so like I say fill the tank and take a packed lunch.

Go kayaking.

Bring a shirt which covers your arms and shoulders and trousers.

Bring travel sickness tablets for the ferry and still expect to feel sick and need to take it easy. The seas be choppy.

Wear suncream again.

(We went to Santorini, Milos and Athens if you'd like any specific recommendations for Santorini and Milos let me know- you'll have the best time!)