Sorry to say but after doing BE in Electronics and Communication you cannot do PG courses in Marine engineering

It requires bachelor's degree in Marine Engineering/Mechanical Engineering /Civil Engineering / Naval architecture.

There are many courses which you can opt after BE in ECE

Scope for higher studies after BE Electronics and Communications
M.Tech in Electronics and Communications
M.Tech in Microelectronics and VLSI
M.Tech in Communication Systems
M.Tech in Electronic Design and Technology
M.Tech in Power Electronics
M.Tech in Computational Statistics
M.Tech in Computer Science (Information System)
M.Tech in Computer Science (IT)
M.Tech in Computer Science (Networks)
M.Tech in Computer Science (Mobile Computing)

Certification courses after BE in Electronics and Communications
Advanced Diploma in DSP System Design
Advanced Diploma in Real Time Operating Systems
Certificate courses in Verilog and VHDL
Certificate program in VLSI design engineering
Diploma in Embedded Systems Design
Diploma in VLSI Design
Diploma in Wireless Technology
Online course on Embedded Systems
Optical Fiber Communications
PG Diploma course in Industrial Automation System Design
Post Graduate Diploma in Wireless and Mobile Computing
Signaling & VoIP Protocol Implementation
Telecom Protocol Development

Job Types
ASIC Design Engineer
ASIC Engineer Trainee
Business Analyst, IT
Developer
Jr. Embedded Engineer
Jr. Software Engineer (Trainee)
Network Support Engineer
Programmer
Software Engineer -.Net
Test / Quality Assurance (QA) Engineer (Computer Software)