I don’t know what the correct Finnish term would be, but perhaps @Sahti-Laine knows the correct name for this term? The idea is to prevent the reduction of foundation support on the seabed caused by pressure fluctuations from waves. I found a short, very illustrative video on the subject:
So, the starting point is likely a fairly traditional-looking cargo vessel with heavy-duty cranes (typically 400t/crane). These are called Heavylift vessels (note: there are also slightly different types of heavy lift vessels that should not be confused with these).
The intention is apparently to modify it so that a pipe can be installed on the vessel, which can be directed close to the foundation on the seabed. From the vessel, rocks would then be lowered to protect the foundation. In addition, the vessel must be able to stay in position quite accurately to avoid damage – there are vessels on the market that already have this capability, and modifying one to do so is not difficult.
Boskalis’ website has a good video that talks about their similar vessels.