Mooring dolphin is one of the components of open sea marine terminal. A thorough knowledge on wave forces on this mooring dolphin is essential for its design. Experimental investigations were carried out on wave loads on an open sea mooring dolphin with vertical slender cylinders and deck in 0.60 m water depth. The deck slab was placed at nine different elevations above and below the still water level (emerged and submerged conditions) to study the effect of deck elevation on wave loads on mooring dolphin due to regular waves. A study on single cylinder is also carried out to compare the forces on mooring dolphin with the forces on single cylinder. Wave force on single cylinder can be calculated by using Morison equation. There is no theoretical method to calculate wave forces on slender cylinders with deck, especially when the deck is in submerged condition. It is found that the in-line and transverse forces are more when the bottom of deck slab is exactly at still water level and reduce significantly when it is submerged or emerged. Mooring dolphin receives maximum slamming force when the deck is in submerged condition.