The result is a good looking and highly manoeuvrable tug fitted out to a high standard, and capable of shiphandling, towage at sea and anchor-handling.

Thetis is 28.80m in length overall, with a moulded breadth of 10.00m and draft of 4.50m.

The hull is heavily constructed, with a transom stern, rounded bilges and a semi-raised forecastle. Plate thickness in the shell, bottom and deck is quoted as 12mm, with plating in the bow of 15mm and the sheerstrake 20mm. Construction has been carried out in compliance with Germanisher Lloyd and Dutch Shipping Inspectorate rules and the vessel carries the classification GL +100 A5 E Tug +MC AUT.

Thetis is powered by two Wartsila 9L20 main engines each rated at 2298 bhp (1690bkW) at 1000rpm. The main engines are coupled, via Twin Disc HD 300-7 slipping clutch units, to a pair of Wartsila - Lips FS250-S/WN-2400 fully azimuthing propulsion units.

Each unit is fitted with a five blade fixed pitch propeller of 2400mm diameter, rotating within a thrust-enhancing nozzle.

On trials the tug achieved a bollard pull of 61 tonnes pulling ahead and 54 tonnes astern.

Results of free running trials were 12.5 knots ahead and 12 knots going astern. Noise levels onboard are reported to be extremely low due to the heavy construction of the vessel and efficient sound insulation. The original specification quoted a Dynasea 'pump-jet' bow thruster, delivering thrust through 360º, but that unit is still to be fitted.

Two Kraaijeveldt towing winches are fitted, both with a maximum brake holding load of 150 tonnes and a line pull of 30 tonnes at 15m/min. The winch on the foredeck is of the single, split drum, type intended for shiphandling and carrying 150m of 48mm diameter steel wire rope on each portion of the drum.

In order to increase stability while towing, fairleads for each towline are incorporated in the forward bulwarks. The aft towing winch also has a single split drum and accommodates a synthetic fibre towline of 200m in length, and for deep sea towing, a 600m towline of 48mm diameter. A small additional drum is added to the starboard side of the winch, with its own roller fairlead, for anchor-handling.

Hydraulically operated stainless steel towing pins are located in the after bulwarks and a stern roller is fitted beneath a demountable section of bulwark.

The latter can be handled by means of the Effer 25.000-3S deck crane mounted adjacent to the starboard exhaust stack.

Three Deutz auxiliary diesels are installed. A Deutz BF 8M 1013 engine drives a pump for the entire deck hydraulics system and a Deutz BF 6M 1013M powers the main auxiliary generator. The latter supplies 120kVA at 230/400v at 50Hz.

A 52kVA harbour set is driven by a Deutz BF 4M 1012E diesel.

The wheelhouse and accommodation are fitted out to a very high standard with considerable use of natural wood in the linings and trim.

Accommodation is provided for up to six persons in four cabins, with all of the normal facilities.

A well-glazed wheelhouse, with full-length windows, gives excellent all round vision and the entire superstructure is designed to give effective clearance when working close alongside ships. A comprehensive bridge electronics package includes navigational and communication equipment suitable for deep sea use and meets the requirements of GMDSS Areas A1, A2 and A3. This includes long and short range Furuno radars type FR-2115B and FR-1505 Mk 3; a Radio Zeeland Seapilot 75 autopilot;

DGPS, Echosounder and Navtex by Furuno and a Quodfish, Chartworks MAP-210 electronic charting and navigation system.