Hi @yuki,
I’m not sure if using the Water Linked DVL and Underwater GPS at the same time is available yet, so I’ve asked internally and will get back to you.
From a quick forum search, I found this mention in 2020 (when the DVL was released)
but I’m unsure how the situation has changed since then.
As I understand it the DVL measurements are sent as visual odometry readings, so you may be able to set the EK3_SRC Parameters to meaningful values yourself that allows automatically combining the GPS and DVL results in the EKF (noting that there are parameters available for setting noise/confidence estimates that can reduce/increase the weighting of the GPS results).
EDIT: EK3 Parameters → EK3_SRC Parameters (with new link)