Sorry, but there are boats built and designed for 'bluewater' sailing, and ones which are not. This is not to say that one cannot cross oceans in a row boat or traverse Niagara Falls in a barrell, only that it is unwise to do so. There are a number of books
on the topic, but if we are talking about monohulls the following seem to be consensus opinions as to what makes a bluewater boat:
1. solid, if not necessarily heavy construction (boats have developed stress cracks and structural failures in heavy seas).
2. a small cockpit with a high bridgedeck, watertight cockpit lockers and at least four 1 1/2" cockpit drains (inevitably the cockpit will be swamped and you do not want water to flood the interior).
3. balance in the rig and hull design so that the boat does not have excessive weather/lee helm
and tracks well (saves wear and tear on both a human helmsman and a windvane/autopilot).
4. substantial spars/rigging with open body turnbuckles (loosing a rig is a disaster offshore).
5. significant rocker in the underbody (as Robert Perry, NA says, it is rocker and not 'U' or 'V' sections in the underbody that avoid pounding in heavy seas.
6. narrower, rather than wider beam for LOA
(assists in righting ability and reduces weatherhelm when healing).
7. moderate freeboard (improves sailing and anchoring
stability in strong winds)
8. an easy to set up and useable emergency
tiller (steering systems can break, and many center cockpit
vessels have emergency
tillers that can only be utilitzed below decks!).
9. strong bow roller for at least 2 anchors and strong bow, stern and spring cleats
10. smaller and stronger portlights/hatches that can withstand knockdowns and worse.
11. adequate handholds below.
12. sufficient sea berths for the anticipated crew.
13. a galley
designed to allow the cook to brace him/herself and a side to side gimballed stove.
14. the ability to sail to windward in heavy sea/wind conditions sufficient to claw
off a lee shore.
16. the ability to heave to.
17. adequate ventilation.
18. a proper chart table/navigation station
19. a well protected rudder
(best is at the end of a full keel
, a skeg is next best).
20 offshore sails
with adequate construction and reefs
for all conditions.
21. positive locks for all cabin doors/floor hatches.
22. adequate tankage for water/fuel for long passages.
23. sufficient storage
space for stores for long passages.
drop boards with positive locking.
The list can go on, and there have been numerous books
written on the subject. No matter how you want to cut it, the above are all important features in a 'bluewater' or offshore
boat. Many boats can be modified to have some, or all of the above features. But regardless, all of the above are features of a true 'bluewater' or 'offshore' sailing monohull
. There IS a difference.