The correct option is B shoal
'Platoon' means a subdivision of a company of soldiers;
'Shoal' is a collective noun which used for large number of fishes;
'Tiding' is a gerund which means work in or out of harbour with the help of the tide;
'Meeting' means an assembly of people for a particular purpose, especially for formal discussion.
Here, fishes are mentioned, therefore the appropriate option to complete the sentence is: B: shoal.