What is the significance of Chhatrapati Shivaji's seal used in the new Navy ensign?

Indian Navy's new ensign bears the seal of the Maratha emperor Chhatrapati Shivaji Maharaj, who is known to have laid the foundation for the modern Navy in India. The blue octagon encasing the National Emblem represents the eight directions, symbolizing the Navy's "multidirectional reach and operational capability". The anchor depicted below the Emblem represents steadfastness, the Navy said.

Prime Minister Modi unveiled the Indian Navy’s new ensign or ‘Nishaan’ during the event to commission India’s first indigenous aircraft carrier INS Vikrant on Friday.
Replacing the previous ensign which displayed the cross of Saint George, a remnant of India’s colonial past, the new Nishaan displays the tricolor on the upper left-hand corner and a blue octagon encasing the national emblem atop an anchor superimposed on a shield with the Navy's motto “Sam No Varuna" in Devanagari on the right side.
The Prime Minister’s Office in a statement said that the new ensign would be “doing away with the colonial past and befitting the rich Indian maritime heritage."

Here’s everything you need to know about the Naval Ensign:

• The Indian Navy’s ensign has changed five times before this. After Independence, in 1950, the ensign was changed with the Indian national flag replacing the Union Jack in the canton (top left corner). In 2001, St. George’s cross was replaced with the naval crest in the middle of the flag but the changes were reversed in 2004 when the cross was brought back along with the Ashoka emblem. In 2014, ‘Satyamev Jayate’ written in Devanagari script was included below the Ashoka emblem.
• The blue octagon encasing the national emblem represents the eight directions and has been included as a symbol of the Navy’s “multidirectional reach and multidimensional operational capability". The anchor below the emblem depicts steadfastness.
• The octagonal shape with twin golden borders is inspired by the seal of Maratha Emperor Chhatrapati Shivaji Maharaj, who had established an impressive naval fleet during his reign.
• The Navy’s motto “Sam No Varuna" — a Vedic mantra invoking Varuna, the god of seas, to be auspicious — has been added in Devanagari.
• The new Nishaan is the culmination of a long-pending demand to make the Naval ensign more Indian and not the upholder of its colonial past. “The Red Cross has nothing to with India’s history. So demands have been made for a change," told an official.