There are several passenger ships that that do the rounds of Lakshadweep islands. These include Amindivi, Arabian Sea, Corals, Kavaratti, Lagoons and Minicoy. MV Kavaratti is the biggest ship with capacity to carry about 700 passengers. All passengers will not be tourists as many locals travel routinely by ships. Each ship has a defined route and some cover 3-4 islands on a round trip to Kochi, each voyage lasting 3 to 5 days. I travelled by MV Kavaratti from Kochi to Agatti.
These ships are a lifeline for the inhabitants of Lakshadweep.
No comparison to cruise ships
At first look, the ship MV Kavaratti looked bigger than my expectation. But there is absolutely no comparison to the cruise ships such as those that run out of Singapore or Hong Kong or those that run in the Mediterranean or Caribbean seas, whether in terms of size or recreation facilities or food options. Alcoholic beverages are also not served.

The ships normally depart in the afternoon from Kochi but tourists are usually required to check in well ahead of time. That gives adequate time to explore the ship before departure. My ship departed late afternoon and just 3-4 hours into the journey, the engine conked off. I waited on the deck until 11PM before giving up. I learnt later it was ~6 hours before the snag could be rectified and the ship could resume its voyage. Luckily, the electricity was not turned off during this time.
Instead of reaching Agatti for breakfast, I reached in time for evening tea!
Transfers by small boat
My ship had two halts in smaller islands before Agatti. In the absence of a jetty, the ship anchored in the open sea and transfer of passengers, luggage and cargo happened by smaller boats. I thought Agatti had a jetty but I too was transferred in a boat.

Cabins are small and facilities limited
There are 3-4 classes of accommodation available but the cabins are a bit cramped. The beds are bunk type even in cabins. First class has two berths and second class 4 berths, but both come with private bathrooms. Food is served in the common cafeteria/dining hall and there is no room service! Which is just as well given the size of the cabins. Food is ok, nothing fancy. Other facilities such as a recreation room or lounge, small pool (often without water!), functional gym, library, etc. may not be available on all the ships.
The time around sunset and sunrise and night time before hitting bed are the best times to be on the deck. I love sitting out on the deck and absorbing the absolute stillness of the night.
Choose ships with minimal stops
The journey was quite smooth as the sea was calm. I definitely enjoyed the short journey though I would not prefer such ships for longer journeys. If you decide to travel by ship, try and choose a trip with minimal stops. Each stop can easily eat up hours.
I have also read that the published timings are often not adhered to by the ships, in many cases for reasons beyond control. If you are travelling back to Kochi by ship and have an onward connection, do make sure you keep adequate buffer.
How to book?
You can make a direct booking online on this website.
http://lakport.nic.in/Home.aspx
One way fare from Kochi to Agatti is ~INR 5K per person in first class, and half of that in second class. The fare in inclusive of all meals and transfer by small boat. This is for MV Kavaratti and the rates may be different for other ships.
Should you consider travel by ship to Lakshadweep?
Consider a journey by ship, either one way or return, for two reasons.
One, you have not travelled by ship over open sea or experienced cruise travel before.
Second, you wish to lower the total cost of holiday.
If you are travelling to islands such as Minicoy or even Kalpeni, there is no other alternative but to travel by ship.