A distinction should be drawn between fixing limits in the sea, which is a unilateral act, and delimitation involving two States with different legal claims to a given maritime area. This definition can be considered as an established fact in international law, as there are many cases handled by the International Court of Justice (ICJ)  in this respect:
— "tracing the exact line or the exact lines of boundary between areas in which are respectively exercised the authority or sovereign powers" of two States (ICJ, case concerning the continental shelf of the Aegean Sea, 1978);
— "no maritime delimitation between two States whose coasts are adjacent or opposite each other may be undertaken unilaterally by either one of these States" (ICJ, case concerning the Gulf of Maine, 1984)…
An operation both complex and technical, but also of a legal and political nature, delimitation may prove to be long, hard to implement and, finally, perceived as an obstacle to any possibility for cooperation between bordering States in one and the same maritime area.
Such a perception needs to be qualified. It can happen that the problem arises due to the very complexity of delimitation itself. It must be admitted, however, that major political conflicts constitute the decisive obstacle rather than maritime delimitation between two States. Delimitation records the level of political discord; it reflects or prolongs it. The case of the dispute between Greece and Turkey, and Israel's relationships with certain Arab countries, are examples which clearly illustrate this observation.
Maritime delimitation is now seeing more activity due to the trend to create national jurisdiction areas in the sea; it is actively pursued in the case of a continental shelf (CS) due to the economic potential attributed to this submarine area. Progress on the part of geological marine prospection explains the great importance of delimitation from the point of view of a coastal State intending to exercise its sovereign rights over the natural resources of "its" CS. If one considers all the potential offered by marine energy in an Exclusive Ecomic Zone (EEZ), the living resources that it contains, one could well say that a "maritime delimitation culture" is developing among different States.
Delimitation thus forms part of a diplomatic negotiation process. When it is successful and satisfactory for both of the States concerned, it is seen as a stabilizing factor in bilateral and regional relations, but also at international level. The publicity surrounding the result of a delimitation procedure enables the various participants, governmental or otherwise, to learn about the legal status of the area of in which they sail or fish, carry out research, prospection, exploration or exploitation, all activities covered by national jurisdiction upon which maritime delimitation throws new light.
The challenge implied by negotiations (their duration, absence of) is not in itself an obstacle to proceedings undertaken by the two States to initiate cooperation in the area which is to be delimited and over which they are in dispute. Except in the case of a major conflict of interest, such cooperation is always possible; it is all a matter of circumstances: protection and preservation of the marine environment are the fields with the highest potential for cooperation, especially if such cooperation is encouraged from outside by an international organization, through instruments such as a directive from the European Union  - which can be somewhat restrictive.
In a sensitive context for maritime delimitation, cooperation disposes of a basis within the Convention for both the EEZ  and the CS . Drafted in identical terms, these two articles point to two possibilities: either "a temporary arrangement of a practical nature" or "not to compromise or hamper" the achievement of a permanent agreement. Acting together, even temporarily, or abstaining from any activity alone. Delimitation essentially concerns States involved in overlapping maritime areas. They must reach a solution by means of an agreement, and the solution must be fair, in conformity with international law, even if few indications exist in international conventions.
 Directive dated July, 2008, concerning a strategy for the marine environment, an article which takes note of the limits of national jurisdiction of Member States in order for conditions to be set up for ascertaining the good ecological state of the marine environment.
The Mediterranean is here the subject of a sub-regional approach distingusihing three basins:
— the western Mediterranean,
— the Ionian Sea and central Mediterranean,
— the Aegean and Levantine Seas.