The plural of ocean is oceans.
The possessive form for the noun sea is sea's.Example: The sea's power should never be underestimated.
The plural is oceans and the plural possessive is oceans' (referring to more than one ocean).
Water doesn't really have a plural form, other then 'Waters', eg. 'The waters of Life', 'The waters of this ocean...'
The singular form of the plural noun oceans is ocean.The singular possessive form is ocean's.Example: You can check the chart to find the ocean's depth here.
There is no plural form. Do and Do not are verbs
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
The plural form of "is" is "are."
The plural form of "was" is "were."
The plural form of "I" is "we."
"Groceries" is the plural form of "grocery."