## 3 Results  
### Pockmark Field  
#### 3.1.1 Pockmark Distribution, Size and Shape  
Multibeam bathymetric data revealed the presence of numerous seabed depressions, which make up an impressive pockmark field (Figure 3). The field covers a well-delimited area of 2.4 km\({}^{2}\) between the 17 and 45 m isobaths. The use of the MBES led to the accurate and complete mapping of the pockmarks in comparison to the previous surveys, where the mapping was based on the use of the single beam echosounder and sparse datasets of sub-bottom profiler and side-scan sonar [39; 40; 41; 42; 57]. The number of pockmarks obtained in the present study was ninety-two (92), which occupy an area of 0.41 km\({}^{2}\), approximately 20% of the entire extent of the field, which is much higher than the seventy-two (72) pockmarks obtained previously [42; 57]. Twenty-three (23) out of the seventy-two (72) previously recorded pockmarks are now completely buried under the breakwater and the docks of the new harbour (Figure 3). Moreover, the comparison of the datasets showed that three (3) pockmarks identified and mapped in the present study were wider and have been partially covered. This finding increases the number of the field's pockmarks to 115--92 well-formed and 23 completely covered by the harbour installations. The pockmarks, according to their morphological characteristics, can be distinguished into three main morphological classes (Table 1):  
* Unit pockmarks: they have a diameter of 8 to 20 m, and their relative depth, compared to the surrounding seabed, varies from 1 to 5 m. They are small in size, and they could be considered early stages of development (Figure 3a,c). * Normal pockmarks: they are circular or ellipsoidal in plan view, the diameter ranges from 20 to 130 m, and their relative depth reaches 14 m. These pockmarks can be characterised as being in a mature stage of development (Figure 3a,d). * Composite or complex pockmarks: they have an irregular shape in plan view, their size is large and reaches a perimeter of 805 m, and their relative depth reaches up to 20 m. They are pockmarks that resulted from the amalgamation of neighbouring normal and unit pockmarks (Figure 3a,e). The geographical distribution of the pockmarks, both well-formed and covered by the harbour construction, shows that the field can be divided into two main sectors of about the same seafloor extent (\(\sim\)1 km\({}^{2}\)) (Figure 3a). Though the average spatial density of the total field is 50 pockmarks/km\({}^{2}\), the northern sector includes 55 pockmarks, while the southern sector includes 31 pockmarks, suggesting a higher density of pockmarks in the northern sector of the PGPF in relation to the southern one. Furthermore, the number of pockmark occurrences is higher south of AT.F and at the shallow part of the southern sector (Figure 3a; HD1 and HD2, respectively). The northern limit of the pockmark field is very well-delimited and corresponds to the offshore continuation of the active fault of Agia Triada (see also Section 3.1.5). Surprisingly, six small pockmarks were recorded further to the north of the AT.F lineament, which has never been reported in the previous surveys. The assumption that these pockmarks developed in the last 15 years seems rather weak, and their recording should be attributed to the best resolution systems in the present survey. Within the field, the pockmarks appear to form \"clusters\" (Figure 3d), which are usually collinear \"chains\" (Figure 3f). Collinear pockmarks may occur for several hundred meters. A large pockmark, or the joining of two, may occur at the end of such \"chains\" of pockmarks (Figure 3).