Exegesis:
ochlos pleistos ‘a very large crowd,’ ‘a huge crowd’: pleistos is the superlative of polus ‘many,’ ‘much.’
sunagetai (cf. 2.2) ‘gathers together,’ ‘collects’ (cf. 3.20).
hōste auton … kathēsthai (cf. 1.27 for this construction) ‘so that he … sat.’
eis ploion embanta ‘having entered a boat’: the two clauses together may be translated as coordinate: ‘so that he entered a boat and sat (in it).’
embainō (5.18; 6.45; 8.10, 13) ‘enter’: in Mark used only in connection with a boat: ‘embark.’
en tē thalassē ‘in the sea’ (i.e. the Lake of Galilee: cf. 1.16): the words are connected with kathēsthai ‘he sat in the Lake,’ but the meaning is clear enough. Jesus was in (or, on) the Lake, seated in a boat, while the crowd was pros tēn thalassan ‘on the beach,’ ‘near the water,’ epi tēs gēs ‘on land.’
en ‘on.’
(Note: care should be taken to avoid the error into which several translations have fallen, namely, that of having Jesus sitting in the water! Most English translations say simply ‘on the water,’ no misunderstanding resulting. Some, however, use a descriptive phrase: The Modern Speech New Testament ‘a little away from the land’; Manson ‘lie off-shore’; cf. O Novo Testamento de Nosso Senhor Jesus Cristo. Revisdo Autorizada ‘pulling away from the beach.’)
pros tēn thalassan ‘by the sea-side’ i.e. on the shore.
Translation:
Beside the sea must be specific in some languages, i.e. ‘on the shore, along the lake,’ or ‘at the mouth of the sea’ (Conob).
It is essential that one be consistent in the size and shape of boats depicted as being used on the Lake of Galilee (cf. 1.19).
In order to avoid the common mistake of having Jesus sit down in the water, it is necessary in some languages to specify that ‘he got into a boat which was floating in the water and he sat down.’ After all, it is possible to get into a boat which has been drawn up onto the shore, hence this detailed rearranging of the semantic components is required in some languages (e.g. Chicahuaxtla Triqui, Barrow Eskimo, Central Mazahua, and Kekchi).
In a number of languages there is no ambiguous way of speaking about the crowd as ‘being beside the sea on the land.’ One must specify whether the people were seated, standing, moving about, etc. In general it is preferable to employ a word meaning ‘to be seated,’ since this is often also the most generic term indicating ‘to be in a place.’
Quoted with permission from Bratcher, Robert G. and Nida, Eugene A. A Handbook on the Gospel of Mark. (UBS Handbook Series). New York: UBS, 1961. For this and other handbooks for translators see here .