Tips to help you decide what liveaboard diving vacation is best for you.

Hull:

• A boat with a long narrow hull will be fast whereas a wider hull, such as a catamaran is more stable.
• A wooden hull sits high in the water and is more affected by the sea conditions
• A steel hull sits lower in the water and as it's heavier than wood will be slower.

Compressors:

• Two high-pressure compressors.
• Low-pressure compressors to supply Nitrox (many liveaboards offer Nitrox for free) 
• High-pressure oxygen supplies for diving emergencies.
• If you want to use trimix, check that the vessel carries sufficient helium, and check the cost.

Generators:

• 2 generators should be available, switching from one to the other.
• Check what voltage is available for re-charging etc.

Engines:

• 2 engines give more manoeverabilty and provides a backup.

Safety Features:

• GPS and Radar are a must.
• A powerful marine VHF radio to keep in touch especially when there is no mobile phone signal.
• Life rafts, life jackets and Emergency Position Indicating Radio Beacons

Entry and Exit:

• It needs to be easy and safe.

Dive Deck:

• A purpose-built dive deck with sufficient space for all the divers.
• Personal storage space for gear.
• Your tank will need to be filled where it is stowed, and this job must be carried out securely, so that a rolling vessel doesn't tip everything onto the deck.
• Is there a freshwater shower and nearby toilet?

Accommodation:

• How spacious are the cabins and do they have air con?
• Is there a watermaker?
• What entertainment is there on board? (DVDs, video screen, etc)
• Food - this can make or break the enjoyment of your trip, regardless of how good the diving is.

Tenders:

• Are there sufficient tenders for the number of guests?

Photography:

• Is there a dedicated camera room with a dry table area kept just for camera equipment with power facilities?
• Is there a separate freshwater rinse tank for cameras?

Jacuzzis:

• Many boats now boast Jacuzzis. However, remember that being in hot water immediately after diving could lead to skin bends.  [Divers who have been chilled on decompression dives (or dives near the no-decompression limit) and take very hot baths or showers may stimulate bubble formation. Source: www.emedicine.com]

Lastly, the crew.  A good crew can make all the difference to your trip. Check the guide:diver ratio.  A knowledgeable dive guide will make all the difference to your diving.