Marine operations are often developed with the use of numeric simulation, in particular lifting operations and transfer of cargo between different units at sea. The effect of the environmental conditions is often the limiting factor and must be included together with models of different components and sub-systems. This paper describes an approach to synchronize spatial and temporal environment information such as universal constants, current, wind, and wave for use in co-simulations of marine operations. Co-simulation models in marine operations will inherently use physical constants, wind and current velocities to calculate forces. Wind and current velocities can have spatial and temporal variations that require the models to synchronize the values. In the event of simulations in waves, the position of the ocean surface, wave particle velocities must be coherent between individual co-simulation models. Further complicating matters is the case of propulsors that produce forces by creating local currents. This paper suggests a structured description of an environment for co-simulation of marine operations. This is exemplified by the implementation of a co-simulation of an offshore lifting operation where vessel, crane, propulsors and lifting load are all integrated with a common environment.

Optimization and stress testing are key aspects of the design and verification process for large, high-risk systems. Optimization is about improving the capabilities and performance of a system; stress testing is about uncovering its weaknesses and faults. Both require a quantitative representation of the system's behavior, and for complex, multi-physical systems, co-simulation can be a very powerful method to create such a representation. However, co-simulation frequently involves the use of black-box subsystem models, which poses challenges to traditional optimization and stress testing methods. Here, we review the state of the art in co-simulation-based optimization and stress testing, focusing especially on \emph{adaptive stress testing} in the latter case, and discuss open research questions and promising research directions. In particular, we make the case that a co-simulation is not an entirely black box even when some or all of its subsystems are; it may be possible to exploit the visible system structure, coupling variable values, and partial subsystem information. We use examples from the maritime industry to motivate and illustrate the discussion, centering on the highly contemporary design case of an autonomous ferry.